Proper Rendering of Transparent/Glowing Materials

Support Basics & Interface
#1

http://img111.imageshack.us/img111/3630/transemit9wb.th.jpg

You see, I have trouble getting the materials to render like I want. There are four cubes in the above image. The small floating one and the one to the far right have the default texture. The white one is emtting light(0.5) and the one on the left is 50% transparent with raytrans checked. Here are my questions.

  1. This is a minor one. Where the shadow is cast on the white cube it loses its definition line (where the wireframe would be). Does this look strange or is it ok?

  2. The shadow cast by the white cube should be a little lighter because it is emitting light, how come it is still black? And there should be some glow around the cube emitting light, including lighting up the side of the cube next to it.

  3. For the transparent cube, you see that it’s shadow is black, when really it should have some of the light shining through from the lamp. Ideally the light would get refracted/reflected and make a neat shadow with concentrated light spots.

  4. For the transparent cube, you can see that the back is not well defined when it should be for a transparent material. Right now it looks like an opaque green cube, not a transparent grey cube.

#2

This is a minor one. Where the shadow is cast on the white cube it loses its definition line (where the wireframe would be). Does this look strange or is it ok?

This is because of the emit value and is to be expected. I gather that your are using the internal renderer.

The shadow cast by the white cube should be a little lighter because it is emitting light, how come it is still black? And there should be some glow around the cube emitting light, including lighting up the side of the cube next to it.

The emit value only effects the material of the object itself. If you want it to actually light up stuff around it you have to use radiosity if you use the internal renderer. I’m not sure how yafray handles this. The glow around the cube would be caused by the atmosphere in real life and in cg it is usually faked in post processing or by adding a halo material.

For the transparent cube, you see that it’s shadow is black, when really it should have some of the light shining through from the lamp. Ideally the light would get refracted/reflected and make a neat shadow with concentrated light spots.

You have to use ray transparency rather than ztrans to get refraction and proper shadows through a transparent material. The concentrated light spots are called caustics and can only be faked with the internal renderer. Yafray will give you proper caustics.

For the transparent cube, you can see that the back is not well defined when it should be for a transparent material. Right now it looks like an opaque green cube, not a transparent grey cube.

Looks like you used ztrans and the green background is showing through although I can’t be sure from the picture.

GreyBeard

#3

:smiley:

Thank you so much Mr. Greybeard. I love your video tutorials.

Investigating the transparency thing further, I start the default scene and take these exact steps.

F5, alpha->0.5, turn on raytrans, F12

And the render still looks like a solid cube. :frowning:

#4

F5, alpha->0.5, turn on raytrans, F12

And the render still looks like a solid cube.

Two possibilities

  1. you don’t have “Ray” beside the “Render” button depressed.

or

  1. You have “shadow” button in the material “shaders” panel selected. Deslect it.

This is about what you can expect out of the box with the internal renderer (although the shadows could be much better). If you require more realism you have to use yafray.

http://members.shaw.ca/rjplus/glass.jpg

GreyBeard

#5

Well, I’m very sorry to keep coming back. I am getting it so I can make a box translucent, but the shadow is still pitch black. The shadow button was checked by default, so I turned it off and miracles happened :slight_smile:

I’m pretty sure the renderer should see that some light should pass from the lamp through the translucent materials and cast a shadow that is not completely black.

Here is a very simple scene (the default with a translucent cube and plane in back). Notice the black shadow. Am I wrong that the shadow should be a lighter color?

http://img222.imageshack.us/img222/8057/testtrans2rk.th.jpg

#6

What I would do is select the things you want to have the transparent shadow on (the plane) and go to the materials tab and press “TraShadow” so it will recive transparent shadows.

#7

For the material of the plane, if I turn off shadow and turn on “trashad” then I get no shadows at all.

#8

http://img207.imageshack.us/img207/8665/test1va.jpg
Here is my test with these settings. The settings are for the cube, the only thing that is different than the defalt setting on the plane is “trashad” is on.
http://img223.imageshack.us/img223/5870/test28az.jpg

Umm, hope that helps.

#9

Ok, I guess it works :smiley:

I had to turn the alpha down on the cube to see the difference from pure black.

Thanks a bundle

#10

I don’t think you need raytrans depth =10. Usually around 3 or 4 will work in most cases.

#11

gozemem’s “hot metal” thread gives some info on yafray’s capacity to allow objects to act as light sources.

There is a glow plugin for the sequencer that might give a good effect like this… search here at elYsiun for glow and sequencer.