hi
i have an quad model and i try to write image based effects. but i have an little problem in the my vertex shaders.
how can i fit this quad to screen? ( my model is screenalignedquad in the rendermonkey)
sorry for my bad english
hi
i have an quad model and i try to write image based effects. but i have an little problem in the my vertex shaders.
how can i fit this quad to screen? ( my model is screenalignedquad in the rendermonkey)
sorry for my bad english
use a vertexshader like this:
void main(void){
gl_Position = gl_Vertex * 2.0 - 1.0;
gl_TexCoord[0] = gl_Vertex;
}
and draw a quad like that (or replace it by a model):
glBegin(GL_QUADS);
glVertex(1,1);
glVertex(1,0);
glVertex(0,0);
glVertex(0,1);
glEnd();
thanks a lot.
from [-1,1], both x and y on screen, before write gl_Position
It has been suggested that rendering a screen aligned grid (sweet size to be determined per shader) as opposed to a single quad/triangle can be a good thing for performance. Haven’t tried it myself…
Doesn’t the grid mainly help in cases with shader divergence?
But definitely do a triangle which overlaps the screen instead of a quad!
…
some info on grids wrt GPGPU
http://www.graphicshardware.org/previous/www_2007/presentations/nickolls-tesla-gh07.pdf
and for the post processing domain there’s a presentation from gamefest08 lurking about on shader optimization strategies in a similar vein.
…
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