Diffuse transmitter material

[manitwo]

Code: Select all

    <material>
        <name>curtain-difftrans</name>
        <diffuse_transmitter>
            <colour>1 1 1</colour>
            <albedo_texture>
                <uv_set>default</uv_set>
                <path>curtain.jpg</path>
                <b>10</b>         <------------------------ I am talking about this
                <exponent>2.2</exponent>
            </albedo_texture>
        </diffuse_transmitter>
    </material>

As you know the amount of transmitted light of a "diffuse transmitter" is controlled with a texture. In my curtain testscene at first the transmittance was too contrasted (the light flowers let nearly all light through whereas the blue part became nearly black) so i increased the "b" value of the texture to make the transmittance more uniform.
hope this helps

[Stur]

Diffuse transmitter curtain:

It's nice, but is the shadow physically correct ? The curtains' shadow shouldn't be lighter than the wall's one ?

[manitwo]

the problem is that i used a diffuse-transmitter which is >diffuse<, so the transmitted light spreads all over the room. However i could try to use a small noisy-dotted alpha-map to let some "parallel" light-beams through. (which wouldn't be blue tho)
for a more physical accurate curtain you need a curtain with thickness and sss aplied. (which would be slower of course)

[Zom-B]

As you know the amount of transmitted light of a "diffuse transmitter" is controlled with a texture. In my curtain testscene at first the transmittance was too contrasted (the light flowers let nearly all light through whereas the blue part became nearly black) so i increased the "b" value of the texture to make the transmittance more uniform.
hope this helps

yes this helps, thaks mani!

atm the Indigo Manual mentions about a, b & c parameters but there is no explenation

[Kram1032]

C gets rid of pure black (= brightness)
B = contrast, normally strong
A = contrast, extreme...

I dunno, if that's the best explaination (or if it's 100% correct)

[Zom-B]

It seems there is a Problem with the diffuse Transmitter!

Here a (null material blended) diffuse_transmitter rendering:



And here a simple (null material blended)diffuse rendering:



both igi Files are attached!

C gets rid of pure black (= brightness)
B = contrast, normally strong
A = contrast, extreme...

I dunno, if that's the best explanation (or if it's 100% correct)

why does A exist if you could raise B to a veeeeeeerrryyy high number?!
But you explanation helps

[CTZn]

Would the effect be the same if you tesselate the mapped planes further ?

[Kram1032]

hum...
I guess, that's, 'cause of the behaviour of the diffuse transmitter:

it isn't a physically corret thing, but adds light it's own colour.

in that case, the coulour is aded many many times -> no more light :S

[CTZn]

Sounds correct, Kram. So diffuse transmitter is, in most cases, for single layer setups...

[OnoSendai]

As you know the amount of transmitted light of a "diffuse transmitter" is controlled with a texture. In my curtain testscene at first the transmittance was too contrasted (the light flowers let nearly all light through whereas the blue part became nearly black) so i increased the "b" value of the texture to make the transmittance more uniform.
hope this helps

yes this helps, thaks mani!

atm the Indigo Manual mentions about a, b & c parameters but there is no explenation

Actually it's explained exactly what they do in the manual.
It's just hard to understand for non-graphics programmers

[OnoSendai]

ZomB:
there's no problem.
Build the material like this:

mat1 = 50/50 blend of (green) phong and (green) diffuse transmitter.

mat2 = blend of mat1 and a null material. Use the leaf clip map for the blend factor for this material.

[Zom-B]

I'll try this dual Blend later, I just thought the diffuse_transmitter only result above couldn't be right....
its just like the extracted light just adds up to a black color in the center... not very common for light

Actually it's explained exactly what they do in the manual.
It's just hard to understand for non-graphics programmers

He he...

[OnoSendai]

The leaves with the diffuse transmitter look like that because the diffuse transmitter only transmits light - it doesn't reflect it.
General principle: when using a diffuse transmitter, you probably want to blend it with a reflecting material such as a phong or diffuse.

[Zom-B]

The leaves with the diffuse transmitter look like that because the diffuse transmitter only transmits light - it doesn't reflect it.

hmmm... ok... maybe I'am stupid, but if they doesn't reflect the sunlight,
but only transmits light, why aren't the leaves in the middle as bright as the one on the sides...
doesn't the have to look much more uniform brightened?!

sorry if I don't understand this right

[OnoSendai]

They're darker in the middle, because each time light passes through the leaf, it's attenuated (multiplied) by the texture colour. So less light passes through. More leaves -> less light -> darker.