mat3 or mat4 uniform - Forum Open Cascade Technology

Ivan Poberezhnyk
Sat, 12/13/2025 - 03:01

Forums:

Is there any way to set mat3 or mat4 uniform into my custom fragment shader?
Graphic3d_ShaderProgram::PushVariable supports only a limited set of types :(

gkv311 n
Tue, 12/16/2025 - 08:01

Not without patching OCCT as far as I can see:

OpenGl_VariableSetterSelector::OpenGl_VariableSetterSelector()
{
  // Note: Add new variable setters here
  mySetterList = OpenGl_HashMapInitializer::CreateListOf<size_t, OpenGl_SetterInterface*>
    (Graphic3d_UniformValueTypeID<int>::ID,          new OpenGl_VariableSetter<int>())
    (Graphic3d_UniformValueTypeID<float>::ID,        new OpenGl_VariableSetter<float>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec2>::ID,  new OpenGl_VariableSetter<OpenGl_Vec2>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec3>::ID,  new OpenGl_VariableSetter<OpenGl_Vec3>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec4>::ID,  new OpenGl_VariableSetter<OpenGl_Vec4>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec2i>::ID, new OpenGl_VariableSetter<OpenGl_Vec2i>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec3i>::ID, new OpenGl_VariableSetter<OpenGl_Vec3i>())
    (Graphic3d_UniformValueTypeID<OpenGl_Vec4i>::ID, new OpenGl_VariableSetter<OpenGl_Vec4i>());
}

I suggest defining as set of vec3/vec4 uniforms instead and pack them into mat3/mat4 within the shader, if you are not willing to make modifications in OCCT.

in vec3 uMat0;
in vec3 uMat1;
in vec3 uMat2;
...
void main() {
  mat3 aMat = mat3(uMat0, uMat1, uMat2);
  ...
}

Make sure to check row or column-major order expectations.