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magnum/src/Magnum/Shaders/Line.vert

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Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
/*
This file is part of Magnum.
Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
It's 2023 already!
3 years ago
2020, 2021, 2022, 2023 Vladimír Vondruš <mosra@centrum.cz>
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/
#if !defined(GL_ES) && !defined(NEW_GLSL)
#extension GL_EXT_gpu_shader4: require
#endif
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
#if defined(SHADER_STORAGE_BUFFERS) && !defined(GL_ES)
#extension GL_ARB_shader_storage_buffer_object: require
#endif
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
/* Use the noperspective keyword to avoid artifacts in screen-space
interpolation if perspective projection is used in 3D. If not available,
it's worked around by dividing gl_Position with gl_Position.w (which is
extra instructions, so the noperspective keyword is preferred). */
#ifndef GL_ES
#define CAN_USE_NOPERSPECTIVE
Shaders: clean up redundant preprocessor elif condition in a shader.
3 years ago
#elif defined(GL_NV_shader_noperspective_interpolation)
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
#extension GL_NV_shader_noperspective_interpolation: require
#define CAN_USE_NOPERSPECTIVE
#endif
#ifdef MULTI_DRAW
#ifndef GL_ES
#extension GL_ARB_shader_draw_parameters: require
#else /* covers WebGL as well */
#extension GL_ANGLE_multi_draw: require
#endif
#endif
#ifndef NEW_GLSL
#define in attribute
#define out varying
#endif
#ifndef RUNTIME_CONST
#define const
#endif
/* Uniforms */
/* This one is for both classic and UBOs, as it's usually set globally instead
of changing per-draw */
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 0)
#endif
uniform lowp vec2 viewportSize; /* defaults to zero */
#ifndef UNIFORM_BUFFERS
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 1)
#endif
#ifdef TWO_DIMENSIONS
uniform highp mat3 transformationProjectionMatrix
#ifndef GL_ES
= mat3(1.0)
#endif
;
#elif defined(THREE_DIMENSIONS)
uniform highp mat4 transformationProjectionMatrix
#ifndef GL_ES
= mat4(1.0)
#endif
;
#else
#error
#endif
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 4)
#endif
uniform mediump float width
#ifndef GL_ES
= 1.0
#endif
;
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 5)
#endif
uniform mediump float smoothness
#ifndef GL_ES
= 0.0
#endif
;
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 6)
#endif
uniform mediump float miterLimit
#ifndef GL_ES
/* cos(2*asin(1.0/4.0)), with 4 being the documented length limit */
= 0.875
#endif
;
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
/* Uniform / shader storage buffers */
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
#else
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
/* For SSBOs, the per-draw and material arrays are unbounded */
#ifdef SHADER_STORAGE_BUFFERS
#define DRAW_COUNT
#define MATERIAL_COUNT
#define BUFFER_OR_UNIFORM buffer
#define BUFFER_READONLY readonly
#else
#define BUFFER_OR_UNIFORM uniform
#define BUFFER_READONLY
#endif
/* With SSBOs DRAW_COUNT is defined to be empty, +0 makes the condition not
cause a compile error */
#if defined(SHADER_STORAGE_BUFFERS) || DRAW_COUNT+0 > 1
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 1)
#endif
uniform highp uint drawOffset
#ifndef GL_ES
= 0u
#endif
;
#else
#define drawOffset 0u
#endif
layout(std140
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
#if defined(EXPLICIT_BINDING) || defined(SHADER_STORAGE_BUFFERS)
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
, binding = 1
#endif
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
) BUFFER_OR_UNIFORM TransformationProjection {
BUFFER_READONLY highp
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
#ifdef TWO_DIMENSIONS
/* Can't be a mat3 because of ANGLE, see DrawUniform in Phong.vert for
details */
mat3x4
#elif defined(THREE_DIMENSIONS)
mat4
#else
#error
#endif
transformationProjectionMatrices[DRAW_COUNT];
};
struct DrawUniform {
highp uvec4 materialIdReservedObjectIdReservedReserved;
#define draw_materialIdReserved materialIdReservedObjectIdReservedReserved.x
#define draw_objectId materialIdReservedObjectIdReservedReserved.y
};
layout(std140
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
#if defined(EXPLICIT_BINDING) || defined(SHADER_STORAGE_BUFFERS)
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
, binding = 2
#endif
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
) BUFFER_OR_UNIFORM Draw {
BUFFER_READONLY DrawUniform draws[DRAW_COUNT];
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
};
struct MaterialUniform {
lowp vec4 backgroundColor;
lowp vec4 color;
highp vec4 widthSmoothnessMiterLimitReserved;
#define material_width widthSmoothnessMiterLimitReserved.x
#define material_smoothness widthSmoothnessMiterLimitReserved.y
#define material_miterLimit widthSmoothnessMiterLimitReserved.z
};
layout(std140
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
#if defined(EXPLICIT_BINDING) || defined(SHADER_STORAGE_BUFFERS)
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
, binding = 3
#endif
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
) BUFFER_OR_UNIFORM Material {
BUFFER_READONLY MaterialUniform materials[MATERIAL_COUNT];
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
};
#endif
/* Inputs */
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = POSITION_ATTRIBUTE_LOCATION)
#endif
#ifdef TWO_DIMENSIONS
in highp vec2 position;
#elif defined(THREE_DIMENSIONS)
/* Last component is reserved for line distance */
in highp vec3 position;
#else
#error
#endif
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = LINE_PREVIOUS_POSITION_ATTRIBUTE_LOCATION)
#endif
#ifdef TWO_DIMENSIONS
in highp vec2 previousPosition;
#elif defined(THREE_DIMENSIONS)
in highp vec3 previousPosition;
#else
#error
#endif
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = LINE_NEXT_POSITION_ATTRIBUTE_LOCATION)
#endif
#ifdef TWO_DIMENSIONS
in highp vec2 nextPosition;
#elif defined(THREE_DIMENSIONS)
in highp vec3 nextPosition;
#else
#error
#endif
/* Point annotation, matching the LineVertexAnnotation enum bits */
#define ANNOTATION_UP_MASK 1u
#define ANNOTATION_JOIN_MASK 2u
#define ANNOTATION_BEGIN_MASK 4u
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = LINE_ANNOTATION_ATTRIBUTE_LOCATION)
#endif
in lowp uint annotation;
#ifdef VERTEX_COLOR
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = COLOR_ATTRIBUTE_LOCATION)
#endif
in lowp vec4 vertexColor;
#endif
#ifdef INSTANCED_OBJECT_ID
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = OBJECT_ID_ATTRIBUTE_LOCATION)
#endif
in highp uint instanceObjectId;
#endif
#ifdef INSTANCED_TRANSFORMATION
#ifdef EXPLICIT_ATTRIB_LOCATION
layout(location = TRANSFORMATION_MATRIX_ATTRIBUTE_LOCATION)
#endif
#ifdef TWO_DIMENSIONS
in highp mat3 instancedTransformationMatrix;
#elif defined(THREE_DIMENSIONS)
in highp mat4 instancedTransformationMatrix;
#else
#error
#endif
#endif
/* Outputs */
#ifdef CAN_USE_NOPERSPECTIVE
noperspective
#endif
out highp vec2 centerDistanceSigned;
out highp float halfSegmentLength;
#ifdef CAN_USE_NOPERSPECTIVE
noperspective
#endif
out highp float hasCap;
#ifdef VERTEX_COLOR
out lowp vec4 interpolatedVertexColor;
#endif
#ifdef INSTANCED_OBJECT_ID
flat out highp uint interpolatedInstanceObjectId;
#endif
#ifdef MULTI_DRAW
flat out highp uint drawId;
#endif
/* Same as Math::Vector2::perpendicular() */
vec2 perpendicular(vec2 a) {
return vec2(-a.y, a.x);
}
void main() {
#ifdef UNIFORM_BUFFERS
#ifdef MULTI_DRAW
drawId = drawOffset + uint(
#ifndef GL_ES
gl_DrawIDARB /* Using GL_ARB_shader_draw_parameters, not GLSL 4.6 */
#else
gl_DrawID
#endif
);
#else
#define drawId drawOffset
#endif
#ifdef TWO_DIMENSIONS
highp const mat3 transformationProjectionMatrix = mat3(transformationProjectionMatrices[drawId]);
#elif defined(THREE_DIMENSIONS)
highp const mat4 transformationProjectionMatrix = transformationProjectionMatrices[drawId];
#else
#error
#endif
Shaders: add SSBO support to all shaders. For when there's so much to render that it wouldn't fit into an UBO and splitting draw calls and binding buffers under an offset is unwanted overhead.
3 years ago
/* With SSBOs MATERIAL_COUNT is defined to be empty, +0 makes the condition
not cause a compile error */
#if defined(SHADER_STORAGE_BUFFERS) || MATERIAL_COUNT+0 > 1
Shaders: initial implementation of a line shader. The shader requires the input data to be laid out in a rather specific way, and there will be a dedicated MeshTools utility for it in the following commits. For independence though, the shader tests use a custom helper. The initial implementation has certain corner cases which will be eventually resolved. For now they are pinned down with repro cases in the test. But apart from that, it's pretty much usable in practice. Remaining join styles (round and miter-clip) as well as stipple support will eventually follow as well.
4 years ago
mediump const uint materialId = draws[drawId].draw_materialIdReserved & 0xffffu;
#else
#define materialId 0u
#endif
mediump const float width = materials[materialId].material_width;
mediump const float smoothness = materials[materialId].material_smoothness;
highp const float miterLimit = materials[materialId].material_miterLimit;
#endif
#ifdef TWO_DIMENSIONS
highp const vec2 transformedPosition = (transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec3(position, 1.0)).xy;
highp const vec2 transformedPreviousPosition = (transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec3(previousPosition, 1.0)).xy;
highp const vec2 transformedNextPosition = (transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec3(nextPosition, 1.0)).xy;
#elif defined(THREE_DIMENSIONS)
highp const vec4 transformedPosition4 = transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec4(position, 1.0);
highp const vec2 transformedPosition = transformedPosition4.xy/transformedPosition4.w;
highp const vec4 transformedPreviousPosition4 = transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec4(previousPosition, 1.0);
highp const vec2 transformedPreviousPosition = transformedPreviousPosition4.xy/transformedPreviousPosition4.w;
highp const vec4 transformedNextPosition4 = transformationProjectionMatrix*
#ifdef INSTANCED_TRANSFORMATION
instancedTransformationMatrix*
#endif
vec4(nextPosition, 1.0);
highp const vec2 transformedNextPosition = transformedNextPosition4.xy/transformedNextPosition4.w;
#else
#error
#endif
/* Decide about the line direction vector `d` and edge direction vector `e`
from the `pointMarkerComponent` input. Quad corners 0 and 1 come from
segment endpoint A, are marked with the POINT_MARKER_BEGIN_MASK bit and
so their line direction is taken from `nextPosition`, quad corners 2 and
3 come from B and are *not* marked with POINT_MARKER_BEGIN_MASK and so
their line direction is taken from `previousPosition`, with the
direction being always from point A to point B. The edge direction is
then perpendicular to the line direction, with points 0 and 2 marked
with POINT_MARKER_UP_MASK using it directly, while points 1 and 3
don't have POINT_MARKER_UP_MASK and have to negate it:
^ ^
e e
| |
[UP, BEGIN] 0-d--> 2-d--> [UP]
A B
[BEGIN] 1-d--> 3-d--> []
| |
e e
v v
The POINT_MARKER_CAP_MASK is then used below. */
highp const vec2 lineDirection = bool(annotation & ANNOTATION_BEGIN_MASK) ?
transformedNextPosition - transformedPosition :
transformedPosition - transformedPreviousPosition;
mediump const float edgeSign = bool(annotation & ANNOTATION_UP_MASK) ? 1.0 : -1.0;
mediump const float neighborSign = bool(annotation & ANNOTATION_BEGIN_MASK) ? -1.0 : 1.0;
/* Line direction and its length converted from the [-1, 1] unit square to
the screen space so we properly take aspect ratio into account. In the
end it undoes the transformation by multiplying by 2.0/viewportSize
again. */
highp const vec2 screenspaceLineDirection = lineDirection*viewportSize/2.0;
highp const float screenspaceLineDirectionLength = length(screenspaceLineDirection);
/* Normalized screenspace line and edge direction. In case of zero-sized
lines (i.e., points) the X axis is picked as line direction instead, and
thus Y axis for edge direction. */
highp const vec2 screenspaceLineDirectionNormalized = screenspaceLineDirectionLength == 0.0 ? vec2(1.0, 0.0) : screenspaceLineDirection/screenspaceLineDirectionLength;
highp const vec2 screenspaceEdgeDirectionNormalized = perpendicular(screenspaceLineDirectionNormalized);
/* Line width includes also twice the smoothness (because it's a radius
instead of a diameter, and is on both sides of the line), and is rounded
to whole pixels. So for the edge distance we need half of it. */
mediump const float edgeDistance = ceil(width + 2.0*smoothness)*0.5;
#ifdef CAP_STYLE_BUTT
mediump const float capDistance = ceil(2.0*smoothness)*0.5;
#elif defined(CAP_STYLE_SQUARE) || defined(CAP_STYLE_ROUND) || defined(CAP_STYLE_TRIANGLE)
mediump const float capDistance = edgeDistance;
#else
#error
#endif
/* Line segment half-length, passed to the fragment shader. Same for all
four points. */
halfSegmentLength = screenspaceLineDirectionLength*0.5;
/* Calculate the actual endpoint parameters depending on whether we're at a
line cap, line join bevel, line join miter etc.
- `screenspacePointDirection` contains screenspace direction from
`transformedPosition` to the actual point. After undoing the
screenspace projection the sum of the two is written to
gl_Position.
- `centerDistanceSigned` contains signed distance from the edge to
center, passed to the fragment shader. It's chosen in a way that
interpolates to zero in the quad center, and the area where
`all(abs(centerDistanceSigned) <= vec2(halfSegmentLength +
capDistance, edgeDistance))` is inside the line.
- `hasCap` contains `abs(centerDistanceSigned.x)` with a sign
positive if the point is a cap and negative if it isn't. Given
segment endpoints A and B (and quad points 0/1 and 2/3
corresponding to these), the following cases can happen:
- if both have a cap, it's a negative value in both, thus has a
constant negative value in the fragment shader
- if neither have a cap, it's a positive value in both, thus has
a constant positive value in the fragment shader
- if one has a cap and the other not, it's a negative value in
one and positive in the other, interpolating to zero in the
quad center
In the fragment shader, `abs(centerDistanceSigned)` and `sign(hasCap)`
is then used to perform cap rendering and antialiasing. For example,
with a standalone line segment that has square caps on both ends, the
value of `centerDistanceSigned` is like in the following diagram, with
`d` being `halfSegmentLength`, `w` being `edgeDistance`, `c` being
`capDistance`, and an extra margin for `smoothness` indicated by `s` and
the double border:
[-d-c-s,+w+s] [+d+c+s,+w+s]
0-----------------------------2
[-d-c,+w]------------------[+d+c,+w]
| | | | hasCap[0] = hasCap[1] = +d+c+s
[-d-c,0] [0,0] [+d+c,0]
| | | | hasCap[2] = hasCap[3] = +d+c+s
[-d-c,-w]------------------[+d+c,-w]
1-----------------------------3
[-d-c-s,-w-s] [+d+c+s,-w+s]
With a cap only on the left side, `centerDistanceSigned` would be like
this. Note the absence of a smoothness margin on the right side:
[-d-c-s,+w+s] [+d,+w+s]
0---------------------------2
[-d-c,+w]-------------------[+d,+w]
| | | hasCap[0] = hasCap[1] = +d+c+s
[-d-c,0] [0,0] [+d,0]
| | | hasCap[2] = hasCap[3] = -d
[-d-c,-w]-------------------[+d,-w]
1---------------------------3
[-d-c-s,-w-s] [+d,-w-s]
*/
centerDistanceSigned =
/* The the Y coordinate is same for all cases, X coordinate gets
further adjusted below */
vec2(halfSegmentLength*neighborSign, edgeDistance*edgeSign);
highp vec2 screenspacePointDirection;
/* Line join */
if(bool(annotation & ANNOTATION_JOIN_MASK)) {
/* Neighbor direction `nd`, needed to distinguish whether this is the
inner or outer join point. Calculated with basically an inverse of
the logic used to calculate `lineDirection`, with the neighbor
direction always pointing from the A/B endpoint to the other
neighbor line endpoint:
<--nd-0 [BEGIN] [END] 2-nd-->
A B
<--nd-1 [BEGIN] [END] 3-nd--> */
highp const vec2 neighborDirection = bool(annotation & ANNOTATION_BEGIN_MASK) ?
transformedPreviousPosition - transformedPosition :
transformedNextPosition - transformedPosition;
/* Screenspace neighbor direction and its length, calculated
equivalently to screenspace line direction above */
highp const vec2 screenspaceNeighborDirectionNormalized = normalize(neighborDirection*viewportSize/2.0);
/* If the edge direction vector `e` and the neighbor direction vector
`nd` point to the opposite direction (i.e., their dot product is
negative), this is an outer point of the line and a candidate for
a bevel.
^
e
|
-d->-2
|\
B | nd
| \
-----3 v
If a miter join is used instead of a bevel, the point is beveled
only if the line direction `d` and neighbor direction `nd` is
sharper than a limit (i.e., their dot product, or a cosine of their
angle, is between `[-1, -miterLimit]`). */
const bool outerBeveledPoint =
dot(screenspaceEdgeDirectionNormalized*edgeSign, screenspaceNeighborDirectionNormalized) < 0.0
#if defined(JOIN_STYLE_MITER)
&& dot(screenspaceLineDirectionNormalized*neighborSign, screenspaceNeighborDirectionNormalized) < -miterLimit
#elif !defined(JOIN_STYLE_BEVEL)
#error
#endif
;
/* Outer point of a beveled join -- although
https://www.w3.org/TR/svg-strokes/#LineJoin doesn't define *what
exactly* is a bevel, it's defined as "Cuts the outside edge off
where a circle the diameter of the stroke intersects the stroke." at
e.g. https://apike.ca/prog_svg_line_cap_join.html.
0--- ----2a
| |^\
| | e -_
| | |ρ \
A-- ----|--B-e->2b
| | | _-|
| | _- |
| | _- | |
1-- --3 | |
| | |
C
Which ultimately means the `2a` and `2b` quad endpoints are simply
the edge direction vector `e` away from point B, in one case with
the `e` calculated from the AB segment, and in the other from the BC
segment. */
if(outerBeveledPoint) {
screenspacePointDirection = screenspaceEdgeDirectionNormalized*edgeDistance*edgeSign;
/* centerDistanceSigned doesn't need any adjustment, hasCap is set
below for both */
/* Otherwise it's either an outer point of a miter join (basically
points 2a and 2b from above evaluated to the same position), or the
inner point, which is the same for bevel and mitter joins. Given
normalized direction `d` and neighbor direction `nd`,
`normalized(d + nd)` is the "average" direction of the two and `perpendicular(normalized(d + nd))` gives us the direction from B to
2 (or from 3 to B):
0--- --------+---2
| | α/ \
| w | / j \
| |/ \
A-- +_-----d->-B \
| -_ α/α\ \
| -_ / nd \
| d + nd /-_ v \
1---- ----3 -_ \
\ -+
\ \
C
With `2α` being the angle between `d` and `nd`, `α` appears in two
right triangles and the following holds, `w` being the edge distance
from above, and `j` having the length that's needed to scale
`perpendicular(normalized(d + nd))` to get point 2:
|d + nd| w 2 w
sin(α) = -------- = --- --> |j| = --------
2 |d| |j| |d + nd|
Then, vector j is the following, meaning we avoid the normalization
square root completely:
perp(d + nd) (2 w)perp(d + nd)
j = |j| ------------ = -----------------
|d + nd| dot(d + nd)
Point 3 is then just in the opposite direction; for the other side
it's done equivalently. */
} else {
highp const vec2 averageDirection = neighborSign*screenspaceLineDirectionNormalized + screenspaceNeighborDirectionNormalized;
screenspacePointDirection = (perpendicular(averageDirection)*(neighborSign*edgeSign*2.0*edgeDistance/dot(averageDirection, averageDirection)));
/* By projecting the point direction onto the line direction we
get a signed distance from the endpoint, adjust center distance
with that */
centerDistanceSigned.x += dot(screenspacePointDirection, screenspaceLineDirectionNormalized);
}
/* No cap here, store a negative value. TODO If
sign(centerDistanceSigned.x) is different from neighborSign, then
the sign here should be taken based on whether the other point is a
join -- add more bits to the vertex annotation? */
hasCap = -abs(centerDistanceSigned.x);
/* Line cap otherwise -- the quad corner 0/1/2/3 a sum of the signed cap
distance (`cdS`) and signed edge distance vectors (`eDS`), which are
formed by the line direction vector `d` and its perpendicular vector.
Neighbor direction (i.e., the other input from the one used to calculate
`lineDirection`) isn't used at all in this case.
cDS
0<---+----------
| ^
| | eDS
| |
| A--d-->
|
|
|
1---
The signed center distance a sum of half segment length and the cap
distance, multiplied by the cap sign (thus negative for points derived
from A and positive for B). */
} else {
screenspacePointDirection =
screenspaceLineDirectionNormalized*capDistance*neighborSign +
screenspaceEdgeDirectionNormalized*edgeDistance*edgeSign;
/* Add signed cap distance to the center distance */
centerDistanceSigned.x += capDistance*neighborSign;
/* Cap is here, store a positive value */
hasCap = abs(centerDistanceSigned.x);
}
/* Undo the screenspace projection */
highp const vec2 pointDirection = screenspacePointDirection*2.0/viewportSize;
#ifdef TWO_DIMENSIONS
gl_Position = vec4(transformedPosition + pointDirection, 0.0, 1.0);
#elif defined(THREE_DIMENSIONS)
gl_Position = vec4(transformedPosition4.xy + pointDirection*transformedPosition4.w, transformedPosition4.zw);
#ifndef CAN_USE_NOPERSPECTIVE
/* See the CAN_USE_NOPERSPECTIVE macro definition at the top for details */
gl_Position /= gl_Position.w;
#endif
#else
#error
#endif
#ifdef VERTEX_COLOR
/* Vertex colors, if enabled */
interpolatedVertexColor = vertexColor;
#endif
#ifdef INSTANCED_OBJECT_ID
/* Instanced object ID, if enabled */
interpolatedInstanceObjectId = instanceObjectId;
#endif
}