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Simple Fog Problem

Started by Programmer101 Jan 8, 2007 at 4:34 PM 3 replies 1.6k views

Original Post

Jan 8, 2007 at 4:34 PM

Okay, I have just decided to put fog into a program I am making, but all polygons become the fog color with no depth or textures(it seems so simple yet I can't place my finger on it). Here are my present parameters for fog: g_pD3DDevice->SetRenderState(D3DRS_FOGENABLE, TRUE); g_pD3DDevice->SetRenderState(D3DRS_FOGCOLOR, 0x00AAAAAA ); g_pD3DDevice->SetRenderState(D3DRS_FOGTABLEMODE, D3DFOG_LINEAR); g_pD3DDevice->SetRenderState(D3DRS_FOGSTART, 100.0); g_pD3DDevice->SetRenderState(D3DRS_FOGEND, 1000.0); g_pD3DDevice->SetRenderState(D3DRS_FOGDENSITY, 0.1); g_pD3DDevice->SetRenderState(D3DRS_FOGVERTEXMODE, D3DFOG_NONE ); Here is a picture of what I am talking about:

(lol, 4 fps) Thnx

jollyjeffers

245

jollyjeffers

Jan 9, 2007 at 3:43 AM

SetRenderState() doesn't have a floating point overload - the second parameter is always DWORD.

I'm pretty sure if you work through the dword->float binary casting integer values of 100 and 1000 will work out as extremely small floating point values so close to zero as to not matter and therefore fogging your entire display!

Basically you need to pack 32bit IEEE float data as a 32bit unsigned integer:

float fValue = 0.1f; DWORD dwValue = *reinterpret_cast<DWORD*>(&fValue);

ISTR some of the SDK samples used to include a "f2dw" macro that did this conversion in a slightly neater way...

hth
Jack

Programmer101

Author

Programmer101

Jan 9, 2007 at 3:48 PM

Cool, thanks. All I had to do was change my fogstart and fogend to:

g_pD3DDevice->SetRenderState(D3DRS_FOGSTART, *(DWORD *)&vertex_fogstart);
g_pD3DDevice->SetRenderState(D3DRS_FOGEND, *(DWORD *)&vertex_fogend);

I now have a new problem with my fog. I have a semi-sphere for my sky and I want it to blend with the horizon. I was using fog but...when I have fog enabled it fogs out the whole semi-sphere. Does anyone know if I can disable fog for part of the semi-sphere or if I can set the max height for the fog?

Draconis_9

Jan 9, 2007 at 9:35 PM

I've found that if you reduce the fog end and put up the fog density to 0.5ish it works quite well

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