c++ - animating a model without redrawing the whole background drawing --OPENGL -

using opengl , making simple animation small triangle move through path have created mouse (glutmotionfunc).

so problem how can animate small triangle without redrawing whole path using glutswapbuffers();

and ,how can rotate triangle only.

i don't want use overlay switching between these 2 layers takes time.

if redrawing whole path expensive, can rendering off-screen framebuffer. mechanism opengl called frame buffer object (fbo)

explaining how use fbos in detail beyond scope of answer here, should able find tutorials. using functions like:

• glgenframebuffers()
• glbindframebuffer()
• glframebufferrenderbuffer() or glframebuffertexture()

this way, can draw additional triangle fbo whenever new triangle added. show rendering on screen, can copy current content of fbo primary framebuffer using glblitframebuffer().