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Point sprites size

Started by outlawhacker Apr 26, 2006 at 4:51 AM 5 replies 1k views

Original Post

Apr 26, 2006 at 4:51 AM

Hey Ok, so I got alpha going for my point sprites, but now the size gets crap. It's all ok until I get a bit close, when the camera is 3-4 units away from the sprite. When I get closer the sprite is scaled down. This is how i do it:



a_Device->SetRenderState(D3DRS_POINTSPRITEENABLE, TRUE);
a_Device->SetRenderState(D3DRS_POINTSCALEENABLE,  TRUE);
a_Device->SetRenderState(D3DRS_POINTSIZE,       FtoDW(m_Size));
a_Device->SetRenderState(D3DRS_POINTSIZE_MIN,   FtoDW(0.0f));
a_Device->SetRenderState(D3DRS_POINTSCALE_A,    FtoDW(0.0f));   // Default 1.0
a_Device->SetRenderState(D3DRS_POINTSCALE_B,	FtoDW(0.0f));   // Default 0.0
a_Device->SetRenderState(D3DRS_POINTSCALE_C,	FtoDW(1.0f));   // Default 0.0

// Use the particle size
// Example:
vertices->m_Size = particle->m_Size;

// Render...

Any suggestions on what could be wrong are greatly appreciated. Thanks in advance

jollyjeffers

Apr 26, 2006 at 6:13 AM

What sort of values does m_Size contain? It should be a pixel/screen-space measurement iirc.

Also, have you verified that your hardware/drivers allow point-sprite scaling and that you're within any defined limit. My Gf6800 reports '8192' as the maximum point size, but some older hardware uses '1' or '0' to indicate limited/no support.

hth
Jack

domin

Apr 26, 2006 at 6:22 AM

Check for FVFCaps.PSIZE too - it must be 'YES' to manually (per vertex) scale point sprites. If you have 'NO' then turn off HVP.

programmer_tom

Apr 26, 2006 at 11:59 AM

ya, independent scaling (per vertex) isn't always supported through the FFP. do yourself a favor and write a shader so all cards can have this capability.

-programmer_tom

outlawhacker

Apr 26, 2006 at 12:42 PM

Hmm...I checked my card (Gf 6600) and it supports point sprites of size 8192 and it supports changing the size by sending D3DFVF_PSIZE with the FVF.

At some distance it looks fine but when I come close it stops scaling the sprite so that it looks smaller in the world, but same in screen space. I tried changing the size with respect of the camera distance but that did me no good.

Later on I'll check out shaders too.

domin

Apr 26, 2006 at 1:16 PM

When creating device with CreateDevice() pass 4 parameter as D3DCREATE_SOFTWARE_VERTEXPROCESSING. Point sprites should work correctly and you can check in this way that rest of your code works ok.

outlawhacker

Apr 27, 2006 at 11:05 AM

I tried out SVP but no luck with that either. I'll fiddle around with my program tomorrow and look for some weird stuff.

I tried out some examples on the net and none of them changes the size of the point sprite. Why? Is it generally hard to get it to work? A particle system looks so much better when the sprites changes size.

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