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Gammastrahler

Some strange behaviour...

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hi, i have a problem, i hope anyone can help me... my lightmap code makes this strange black rings, look at it: can anyone tell me what causes this ugly pheonomena? thanks Gammastrahler

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Look like you are overestimating the light component incoming from the lightsource, what kind of algo are you using,a ray caster or a radiosity ? , try to look if a value goes over range, the circles look like a 2d function of the type
u=a*sin( omega*t+phi ) , v=b*cos( oemga*t+phi ) , thus giving an elliptical look, also chek in your light model for light attenuation due to distance,i hope it helps
byez.

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here is some source code, i use the lambertian cosine law for the lighting (function of angle between light and lumel, and distance)

as you can see, i check already that the color values don´t exceed 255.


  
// for each lumel

resultColor.Set(0, 0, 0);
for (int k = 0; k < nLights; k++)
{
light = I_MAP->GetLight(k);
lightpos = light->GetPos();
if (lightpos.Front(v0, N)
{
L.Subtract(lightpos, curlumel);
d = lightpos.Distance(curlumel);
L.Normalize();
a = L.Dot(N);
intensity = ((float)light->GetIntensity() * a) / d;

resultColor[0] += light->GetColor()[0] * intensity;
resultColor[1] += light->GetColor()[1] * intensity;
resultColor[2] += light->GetColor()[2] * intensity;
}
}
if (resultColor[0] > 255) resultColor[0] = 255;
if (resultColor[1] > 255) resultColor[1] = 255;
if (resultColor[2] > 255) resultColor[2] = 255;

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This sounds crazy but it almost looks like integer wraparound? Light is getting above 255 and wrapping back to 0? Make sure it is clamped; it looks like you might not being doing it right.

You might do this instead:
if ( resultColor[0] + light->GetColor()[0] * intensity < 255 )
resultColor[0] += light->GetColor()[0] * intensity;
else
resultColor[0] = 255;

Ugly code, but I''m not entirely conscious right now. Anyway, try that. Just a weird idea.

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