The Accumulation buffer

Want to know something evil? It is called the glAccumulation buffer. This will allow you to achieve very basic motion blur, but at the same time it is not the best method of achieving this popular computer graphics effect. Why do we even want motion blur in the first place however? Well, if you swing your arm very fast, your eyes pick up on the movement but it is so fast it appears to be blurred. We can mimic this effect through the use of the glAccumulation buffer or through a shader.

So, what is the glAccumulation buffer exactly? Essentially, instead of doing a gpu based motion blur, the glAccumulation buffer allows us to do a rather simple blur. By placing the accumulation call after all of our primary draws, we can have our motion blur.


glAccum(GL_ACCUM,1.0);
glAccum(GL_RETURN,1.0);
glAccum(GL_MULT,0.45f);

glAccum obtains the R,G,B and A values from the buffer currently selected for reading. GL_RETRUN transfers accumulation buffer values to the color buffer(s) currently selected for writing. GL_MULT multiplies each R,G,B, and A in the accumulation buffer by a value and returns the value to its corresponding accumulation buffer location.

By simply writing those three lines of code after your primary draw, you have basic motion blur.