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Fix #30004: cycles brightness/contrast node issues. The formula used did not work

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very well for colors that can be outside of the 0.0..1.0 range, giving +/- infinity
results.

Now we just use a simple linear contrast factor as proposed by Paolo Sourvinos, and
clamp values to be >= 0, and also make the parameters work more in the 0..1 range
instead of the 0..100 range, to be more consistent with other nodes.
This commit is contained in:
Brecht Van Lommel 2012-02-08 17:09:30 +00:00
parent 8e81da423c
commit b6d12f11fe
1 changed files with 5 additions and 21 deletions
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26
intern/cycles/kernel/svm/svm_brightness.h
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@ -27,28 +27,12 @@ __device void svm_node_brightness(ShaderData *sd, float *stack, uint in_color, u
float brightness = stack_load_float(stack, bright_offset);
float contrast = stack_load_float(stack, contrast_offset);
brightness *= 1.0f/100.0f;
float delta = contrast * (1.0f/200.0f);
float a = 1.0f - delta * 2.0f;
float b;
float a = 1.0f + contrast;
float b = brightness - contrast*0.5f;
/*
* The algorithm is by Werner D. Streidt
* (http://visca.com/ffactory/archives/5-99/msg00021.html)
* Extracted of OpenCV demhist.c
*/
if (contrast > 0.0f) {
a = (a > 0.0f? (1.0f / a): 0.0f);
b = a * (brightness - delta);
}
else {
delta *= -1.0f;
b = a * (brightness + delta);
}
color.x = a*color.x + b;
color.y = a*color.y + b;
color.z = a*color.z + b;
color.x = max(a*color.x + b, 0.0f);
color.y = max(a*color.y + b, 0.0f);
color.z = max(a*color.z + b, 0.0f);
if (stack_valid(out_color))
stack_store_float3(stack, out_color, color);