non rectangular scissor, how ??

OpenGL OpenGL: Advanced Coding
1

Is there a way to acheive scissor effect with non rectangular shapes ??

2

You can use the stencil buffer.

3

use the stencil buffer:

.
draw your scene first…
.

glClearStencil(0);
glClear(GL_STENCIL_BUFFER_BIT);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS,1,1);
glStencilOp(GL_REPLACE,GL_REPLACE,GL_REPLACE);

.
draw your clipping-shape
.

// to draw inside the clipping shape…
glStencilFunc(GL_EQUAL,1,1);
// to draw outside the clipping shape use:
// glStencilFunc(GL_NOTEQUAL,1,1);

glStencilOp(GL_KEEP,GL_KEEP,GL_KEEP);

.
draw the part out your scene inside the clipping-shape
.

glDisable(GL_STENCIL_TEST);

that’s all.
btw.: if you have only one clipping-shape to draw, you probably should clear the stencil buffer together with the other buffers within one single glClear call.