magnum/src/Magnum/Shaders/MeshVisualizer.geom

/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019
              Vladimír Vondruš <mosra@centrum.cz>

    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.
*/

#ifndef RUNTIME_CONST
#define const
#endif

#ifdef GL_ES
#extension GL_EXT_geometry_shader: require
#ifdef GL_NV_shader_noperspective_interpolation
#extension GL_NV_shader_noperspective_interpolation: require
#endif
#endif

#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 5)
#endif
uniform lowp vec2 viewportSize; /* defaults to zero */

layout(triangles) in;

#if (defined(TANGENT_DIRECTION) || defined(BITANGENT_DIRECTION) || defined(NORMAL_DIRECTION)) && defined(WIREFRAME_RENDERING)
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 1)
#endif
uniform lowp vec4 color
    #ifndef GL_ES
    = vec4(1.0, 1.0, 1.0, 1.0)
    #endif
    ;

#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 2)
#endif
uniform lowp vec4 wireframeColor
    #ifndef GL_ES
    = vec4(0.0, 0.0, 0.0, 1.0)
    #endif
    ;
#endif

#if defined(TANGENT_DIRECTION) || defined(BITANGENT_DIRECTION) || defined(NORMAL_DIRECTION)
#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 8)
#endif
uniform lowp float lineWidth
    #ifndef GL_ES
    = 1.0
    #endif
    ;

#ifdef EXPLICIT_UNIFORM_LOCATION
layout(location = 4)
#endif
uniform lowp float smoothness
    #ifndef GL_ES
    = 2.0
    #endif
    ;
#endif

#ifdef TANGENT_DIRECTION
in highp vec4 tangentEndpoint[];
#endif
#ifdef BITANGENT_DIRECTION
in highp vec4 bitangentEndpoint[];
#endif
#ifdef NORMAL_DIRECTION
in highp vec4 normalEndpoint[];
#endif

layout(triangle_strip, max_vertices = MAX_VERTICES) out;

/* Interpolate in screen space (if possible) */
#if !defined(GL_ES) || defined(GL_NV_shader_noperspective_interpolation)
noperspective
#endif
out lowp vec3 dist;

#if defined(TANGENT_DIRECTION) || defined(BITANGENT_DIRECTION) || defined(NORMAL_DIRECTION)
out lowp vec4 backgroundColor;
out lowp vec4 lineColor;

void emitQuad(vec4 position, vec2 positionScreen, vec4 endpoint, vec2 endpointScreen) {
    /* Calculate screen-space locations for the bar vertices and form two
       triangles out of them. In case TBN is rendered alone, half bar width is
       lineWidth + smoothness to allow for antialiasing, in case it's rendered
       together with wireframe, it's just lineWidth, as antialiasing would
       cause depth order issues.

        3 - e - 1     -S_-w_0__w_S         -w_0__w
        |      /|      | |     | |         |     |
        |     / |      | |    /| |         |    /|
        |    /  |      | |   / | |         |   / |
        |   /   |      | |  /  | |         |  /  |
        |  /    |      | | /   | |         | /   |
        | /     |      | |/    | |         |/    |
        |/      |      |_|_____|_|         |_____|
        2 - p - 0     -S -w 0  w S         -w 0  w

       The edgeDistance is set to a signed half-width for the antialiased case
       and to 0 otherwise. See the fragment shader for details.
    */
    vec2 direction = normalize(endpointScreen - positionScreen);
    #ifdef WIREFRAME_RENDERING
    float edgeDistance = 0.0;
    vec2 halfSide = lineWidth*vec2(-direction.y, direction.x);
    #else
    float edgeDistance = lineWidth + smoothness;
    vec2 halfSide = edgeDistance*vec2(-direction.y, direction.x);
    #endif

    /* 0 */
    dist = vec3(-edgeDistance);
    gl_Position = vec4((positionScreen - halfSide)*position.w/viewportSize, position.zw);
    EmitVertex();

    /* 1 */
    dist = vec3(-edgeDistance);
    gl_Position = vec4((endpointScreen - halfSide)*endpoint.w/viewportSize, endpoint.zw);
    EmitVertex();

    /* 2 */
    dist = vec3(edgeDistance);
    gl_Position = vec4((positionScreen + halfSide)*position.w/viewportSize, position.zw);
    EmitVertex();

    /* 3 */
    dist = vec3(edgeDistance);
    gl_Position = vec4((endpointScreen + halfSide)*endpoint.w/viewportSize, endpoint.zw);
    EmitVertex();

    EndPrimitive();
}
#endif

void main() {
    /* Screen position of each vertex */
    vec2 p[3];
    #ifdef TANGENT_DIRECTION
    vec2 t[3];
    #endif
    #ifdef BITANGENT_DIRECTION
    vec2 b[3];
    #endif
    #ifdef NORMAL_DIRECTION
    vec2 n[3];
    #endif
    for(int i = 0; i != 3; ++i) {
        p[i] = viewportSize*gl_in[i].gl_Position.xy/gl_in[i].gl_Position.w;
        #ifdef TANGENT_DIRECTION
        t[i] = viewportSize*tangentEndpoint[i].xy/tangentEndpoint[i].w;
        #endif
        #ifdef BITANGENT_DIRECTION
        b[i] = viewportSize*bitangentEndpoint[i].xy/bitangentEndpoint[i].w;
        #endif
        #ifdef NORMAL_DIRECTION
        n[i] = viewportSize*normalEndpoint[i].xy/normalEndpoint[i].w;
        #endif
    }

    #ifdef WIREFRAME_RENDERING
    /* Vector of each triangle side */
    const vec2 v[3] = vec2[3](
        p[2]-p[1],
        p[2]-p[0],
        p[1]-p[0]
    );

    /* Compute area using perp-dot product */
    const float area = abs(dot(vec2(-v[1].y, v[1].x), v[2]));

    /* Add distance to opposite side to each vertex */
    for(int i = 0; i != 3; ++i) {
        dist = vec3(0.0, 0.0, 0.0);
        dist[i] = area/length(v[i]);
        #if defined(TANGENT_DIRECTION) || defined(BITANGENT_DIRECTION) || defined(NORMAL_DIRECTION)
        backgroundColor = color;
        lineColor = wireframeColor;
        #endif
        gl_Position = gl_in[i].gl_Position;
        EmitVertex();
    }

    EndPrimitive();
    #endif

    #if defined(TANGENT_DIRECTION) || defined(BITANGENT_DIRECTION) || defined(NORMAL_DIRECTION)
    backgroundColor = vec4(0.0, 0.0, 0.0, 0.0);
    for(int i = 0; i != 3; ++i) {
        #ifdef TANGENT_DIRECTION
        lineColor = vec4(1.0, 0.0, 0.0, 1.0);
        emitQuad(gl_in[i].gl_Position, p[i], tangentEndpoint[i], t[i]);
        #endif

        #ifdef BITANGENT_DIRECTION
        lineColor = vec4(0.0, 1.0, 0.0, 1.0);
        emitQuad(gl_in[i].gl_Position, p[i], bitangentEndpoint[i], b[i]);
        #endif

        #ifdef NORMAL_DIRECTION
        lineColor = vec4(0.0, 0.0, 1.0, 1.0);
        emitQuad(gl_in[i].gl_Position, p[i], normalEndpoint[i], n[i]);
        #endif
    }
    #endif
}