Hi I''m using blending to to obtain the intersection of some pyramids - it''s working but from the side and top view the sides of the pyramid appear opaque. I''ve tried back-face culling which gets rid of the problem it does only show the intersection area as opaque but then when you rotate you can''t see the pyramids - the code is below glDisable(GL_DEPTH_TEST); glEnable(GL_BLEND); glDepthMask(GL_FALSE); glBlendFunc(GL_ONE, GL_SRC_COLOR); glLightfv(GL_LIGHT0, GL_DIFFUSE, BlueLight); glLightfv(GL_LIGHT0, GL_POSITION, BluePos); glTranslatef(0.0, 0.0, 0.5); glRotated(45, 0.0, 0.0, 1.0); glMaterialfv(GL_FRONT, GL_DIFFUSE, DiffuseRef); glMaterialfv(GL_FRONT, GL_SPECULAR, SpecularRef); glMaterialfv(GL_FRONT, GL_SHININESS, ShininessHigh); glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, PyramidSurface); gluCylinder(PyramidVolume, 0.025, (8.5-0.5), (1.4*8.5), 4.0, 1.0); glDepthMask(GL_TRUE); glDisable(GL_BLEND); glEnable(GL_DEPTH_TEST); -any ideas how I can sort this out? - if i just wanted to see the intersected area - how could do this thanx

blending is not as good as the stencil buffer but this''ll still only show you where they overlap on the screen. to find the intersection u need some maths.
try www.Magic-Software.com

http://members.xoom.com/myBollux

quote: Original post by zedzeek

blending is not as good as the stencil buffer but this'll still only show you where they overlap on the screen. to find the intersection u need some maths.
try www.Magic-Software.com

http://members.xoom.com/myBollux

got any examples of using the stencil buffer and how do i work out the maths??

cheers

Edited by - ogl on January 22, 2001 9:57:41 AM

for info about the stencil buffer check glut or the redbook its really quite easy.
maths is a tricky thing.
check out the magic-software site also have a searhc for ''GJK collision detection''

http://members.xoom.com/myBollux