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Asked: 2026-05-27T16:29:25+00:00

Suppose I have the following code: glRotatef(angle, 1.0f, 1.0f, 0.0f); glRotatef(angle, 0.0f, 1.0f, 0.0f);

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Suppose I have the following code:

glRotatef(angle, 1.0f, 1.0f, 0.0f);
glRotatef(angle, 0.0f, 1.0f, 0.0f);
glRotatef(angle, 0.0f, 0.0f, 1.0f);
glTranslatef(0.0f, 0.0f -5.0f);

Is this less efficient than utilizing one’s own custom matrix via the glLoadMatrix function that accomplishes the same functionality?

Also, I know that when multiplying matrices to form a custom linear transformation, the last matrix multiplied is the first transformation to take place. Likewise, is this the case if I utilize the above code? Will it translate, then rotate about the Z axis, followed by rotations about the y and x axes?

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1 Answer

  1. Editorial Team

    In general if you assemble your matrix on your own and load it via glLoadMatrix or glMultMatrix your program will run faster. Unless you make stupid mistakes in your own matrix routines that ruin the performance of course.

    This is because the glRotate glTranslate etc. functions do quite a bit more than the pure math. They have to check the matrix-mode. glRotate has to deal with cases where the axis is not passed as a unit-vector etc.

    But unless you do this 10thousands times per frame I wouldn’t worry about the lost performance. It adds up, but it’s not that much.

    My personal way of dealing with openGL transformations is to build the matrices in my code and only upload them to OpenGL via glLoadMatrix. This allows me to do lots of shortcuts like reversing the order of multiplications (faster to calculate than the way OpenGL does it). Also it gives me instant access to the matrix which is required if you want to do boundary box checks before rendering.

    Needless to say code written with such an approach is also easier to port onto a different graphics API (think OpenGL|ES2, DirectX, Game-Consoles…)

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