Vertex shader point sprite size question

vvvv beta question
1

Hello everyone,

I wanted to make 2 shaders that could easily be used for showing particles for instance.

In the case where you want to use billboards, point sprites can be faster, but I would like to be able to switch between them without having to tweak anything.

Having inspired my shader heavily on Viktor Vicsek’s point sprite fx, it scales properly perspective-wise, but I am having trouble to get the same scale on every renderer. That is, the viewport size seems to influence the way it looks.

I attached a patch that shows this, and I was wondering if anyone knew how I could get rid of this viewport dependence (if at all possible).

point sprite size control.zip (5.2 kB)

2

pointsprite size is in pixels, and it is dependant on the size of the texture you are rendering it to (vertical resolution i think)
so, pass this value to your shader, and divide psize by it

3

For the interested:

I updated the example, and I guess it scales the way you would expect it now.

It has as the consequence that you need the shader twice, if you have 2 different renderers with different dimensions…

point sprite size control.zip (5.6 kB)