Using a matrix as vertex attribute in OpenGL3 Core Profile

雨燕双飞 提交于 2019-11-29 04:27:12

According to this page and my current implementation of hardware instancing in my game, the proper way it's done is that a mat4 attribute takes up 4 attribute locations. The one you bind and the 3 following.

int pos = glGetAttribLocation(shader_instancedarrays.program, "transformmatrix");
int pos1 = pos + 0; 
int pos2 = pos + 1; 
int pos3 = pos + 2; 
int pos4 = pos + 3; 
glEnableVertexAttribArray(pos1);
glEnableVertexAttribArray(pos2);
glEnableVertexAttribArray(pos3);
glEnableVertexAttribArray(pos4);
glBindBuffer(GL_ARRAY_BUFFER, VBO_containing_matrices);
glVertexAttribPointer(pos1, 4, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 4 * 4, (void*)(0));
glVertexAttribPointer(pos2, 4, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 4 * 4, (void*)(sizeof(float) * 4));
glVertexAttribPointer(pos3, 4, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 4 * 4, (void*)(sizeof(float) * 8));
glVertexAttribPointer(pos4, 4, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 4 * 4, (void*)(sizeof(float) * 12));
glVertexAttribDivisor(pos1, 1);
glVertexAttribDivisor(pos2, 1);
glVertexAttribDivisor(pos3, 1);
glVertexAttribDivisor(pos4, 1);
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