Is there a technical reason why GL_POLYGON_STIPPLE doesn’t slow down rendering at all on my geforceFX at home, but at school on my ATI FireGL X1 it makes rendering very very slow?
I want polygon dithering
Is there a technical reason why GL_POLYGON_STIPPLE doesn’t slow down rendering at all on my geforceFX at home, but at school on my ATI FireGL X1 it makes rendering very very slow?
I want polygon dithering
do you want dithering or stippling? two different things.
i any case, it could be any number of things. it could be some combination of states thats forcing a software path, and so on.
try to be more specific about the conditions, post code, etc.
Ok, I thought that dithering was when a polygon is displayed like this:
http://pages.cpsc.ucalgary.ca/~cherlin/glboard.png
But either way that is the effect I want. Perhaps you could give me the correct name of this as well?
As for code, well, It is just like:
glEnable(GL_POLYGON_STIPPLE);
(render some models via GL_TRIANGLE_STRIP)
glDisable(GL_POLYGON_STIPPLE)
(render some models via GL_TRIANGLE_STRIP)
glEnable(GL_POLYGON_STIPPLE);
(render some models via GL_TRIANGLE_STRIP)
etc
However, I have vertex and fragment shaders running using during all of this
Joseph, i dont know what to tell you about the speed hit. probably a software path on that fire gl, dunno, not familiar with that card.
dithering is briefly discussed in the redbook (chapter 5, skip down a bit):
http://www.parallab.uib.no/SGI_bookshelves/SGI_Developer/books/OpenGL_PG/sgi_html/ch05.html
basically it allows for an increase in percieved color resolution.
oh, as for the name thing, im thinking “contour”, but im not sure what youre after.
Doubt it is a software path since the shader still works and it is not possible that the shader is being done in software.
–Joseph
vp/fp can be emulated in software. just try disabling dithering – see what happens. try diabling stenciling – see what happens. compare card specs. how many instructions do your shaders have? what’s the maximum number on that card? glGet* is your friend. experiment!
heres a site that gives all kinds of info on various cards: www.delphi3d.com
hope this helps!