Similar to the change done in Corrade, see the commit for details:
878624ac36
Wow, this is probably the most backwards-compatibility code I've ever
written. Can't wait until I can drop all that.
Certain Clang-based IDEs (CLion) "emulate" a compiler by inheriting all
its defines, which means one gets __clang__ defined but also __GNUC__
set to 11 or whatever, breaking all these assumptions.
It limits the support for CMake 3.12+, but it's much less verbose and I
don't expect people to use ancient CMake versions with IDEs like Xcode
or VS anyway, so this should be fine.
Fails spectacularly -- the geometry shader is aware only of instanced
object ID, and of vertex ID not at all. The former was a corner case
TODO while I was adding non-instanced object ID visualization in
033e56ec23 and which I kinda forgot about,
the latter was discovered while trying to fix the former.
Fix in the next commit.
Hah this took a while, as there was no texture scaffolding in place at
all. Thus all this had to be added and tested for the first time:
* 2D textures
* 2D texture arrays
* Texture transformation uniforms
* Texture transformation UBOs
* Instanced texture offset
This also means that MeshVisualizer can be used to visualize arbitrary
(single-channel) integer textures now, not just render meshes with
object ID textures. Yay for feature parity!
Forgot that gl_VertexID includes the base offset in the multidraw
scenarios, so we need to take all vertices into account, not just the
largest view. The wraparound would cause nasty output differences among
drivers.
Mainly to have feature parity with Flat and Phong -- otherwise switching
to draw a wireframe on an instanced mesh would be too annoying. Also, if
we have multidraw there already, why not instancing as well.