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Mr. Wilde
03-13-2013, 08:17 AM
Hi,

I have a very simple test setup, a ground plane, and a transparent plane hovering above it.

For some reason, 100% transparency doesn't make the plane fully invisible. It's still semi transparent, perhaps 95%.

What could be the reason for this? The plane is a single quad. One sided. Raytraced transparency is on. Ray Recursion Limit 6, Ray Precision 6.0, Ray Cutoff 0.01, Shading Samples 1, Light Samples 1.

djwaterman
03-13-2013, 09:45 AM
Hard to say without an image, but has the transparent object still have any specular or reflective values, and I'm assuming your talking about the surface setting transparency and not the object property transparency.

Mr. Wilde
03-15-2013, 03:48 AM
Hard to say without an image, but has the transparent object still have any specular or reflective values, and I'm assuming your talking about the surface setting transparency and not the object property transparency.

It seems fog is the issue.

bcicio
03-15-2013, 07:11 AM
If the transparent object is used in some way but is never to be seen in the animation, you could set it to not be seen by camera.

Lewis
03-15-2013, 08:40 AM
Use Clipmap if you still need fog.

madno
03-15-2013, 12:36 PM
Ran into it as well; seems to happen if reflection > 0
Is it suppossed to do that?

112620

[Edit] forgot to say LW 11.5

Sensei
03-15-2013, 07:30 PM
Ran into it as well; seems to happen if reflection > 0
Is it suppossed to do that?


Yes, of course..

Control reflection too using image alpha in Node Editor to have just Transparent text with reflection.

madno
03-16-2013, 12:14 AM
Ok, that does the trick,

but: if a surface is 100% transparent and IOR = 1, should'nt the transparent area of the polygon be free of reflection without the extra alpha in node editor? I am confused.

112635

Sensei
03-16-2013, 12:20 AM
Reflection can be (and IS in real world) independent from transparency!

Look at water, or glass - you have completely transparent material, but still reflective..

How to merge channels:

double color[ 3 ];
color[ 0 ] = material.diffuse[ 0 ];
color[ 1 ] = material.diffuse[ 1 ];
color[ 2 ] = material.diffuse[ 2 ];
if( material.transparency != 0.0 )
{
color[ 0 ] *= 1.0 - material.transparency;
color[ 1 ] *= 1.0 - material.transparency;
color[ 2 ] *= 1.0 - material.transparency;
color[ 0 ] += material.refraction[ 0 ] * material.transparency;
color[ 1 ] += material.refraction[ 1 ] * material.transparency;
color[ 2 ] += material.refraction[ 2 ] * material.transparency;
}
color[ 0 ] += material.specular[ 0 ];
color[ 1 ] += material.specular[ 1 ];
color[ 2 ] += material.specular[ 2 ];
color[ 0 ] += material.reflection[ 0 ];
color[ 1 ] += material.reflection[ 1 ];
color[ 2 ] += material.reflection[ 2 ];

It's TrueArt's Flatten Material node code.

Sensei
03-16-2013, 12:42 AM
From physics point of view diffuse, reflection and refraction is exactly the same process.
Photon from light source is colliding with proton and electron in material and they're absorbed, then reemitted.
If reemission is going to inside of material (direction of incoming photon is not, or little, disturbed), it's transparent or refractive.
If reemission is going to outside of material (direction of incoming photon is reversed) then it's opaque.
Material at one wave length/frequency can be transparent and at other wave length/frequency can be opaque.

If material is white, it means it's absorbing photons in the all visible wave frequencies, and is reemitting them also on all visible wave frequencies without change.
If material is black, it means it's absorbing photons in the all visible wave frequencies, and is reemitting them in non-visible wave frequencies such as Infrared. If it wouldn't radiate energy, it would go to infinity.

IOR = 1.0 means that light wave going through material has speed equal to c - speed of light in vacuum.
IOR = 1.5 means that speed of light wave traveling through water is v=c/1.5=0.666c. Absorption and reemittion of photons is taking time, slowing down light wave when it's passing through material.

madno
03-16-2013, 06:36 AM
Thanks for explaining. I knew about most of it already but was not sure how it is implemted in LW.

vector
03-16-2013, 11:16 PM
Nice explanation :) !

Sensei
03-17-2013, 01:17 AM
IOR = 1.333 is water
IOR = 1.5 is glass

Sorry for mistake.