light affected by shader of transparency

[arcady]

When a light travels through something, it should be affected by it.

So, for example, if the light shines through a green window, the light coming out the other side should be a mix of green and the original light color, and if it then travels through a second window, it should be affected again.

I'm told that this is another way of saying the light needs to be true-raytraced?

Consider the attached image. The top is what currently happens, the bottom is what should happen (only less grainy than the program I used for it delivered - in effect, we need the clarity of the top image, but the coloration of the bottom).

[Patrick210]

C5Pro has translucency which works the way you are asking for.

[arcady]

Can you prove that with a sample render, because I see it on the feature set for carrara 5, regular and pro, but I do not see it having any effect when I test it.

I put a white spot light inside a sphere. I give that sphere the glass shader and then set translucency up to 85%. I make the color of the glass red.

I put in two cubes, one transparent but colored green, the second default shader. Turn off all light sources but my spot light.

The light shines through the sphere and the green wall and hits the final wall, still white.

Translucency may scatter a light, but it isn't affecting its color. Further, I can set a color on translucency, and that will -change- the light to that color, but it isn't blending in the other elements of a shader, and it isn't blending in the previous lighting from what I can tell.


The light fails to be changed by the color of the objects it passes through. It fails to blend with their shaders.


Prove to me it can be done, and that the people, not just me, who have said it cannot are wrong.


Most renderers today will cause it be blended with the things it passes through, and I am requesting that be added to Carrara.

[Patrick210]

Translucency does combine the color of the light with the color set in the translucency channel. The more transparent your shader is the less effect the color will have on the light. Sometimes it is harder to see the effect of combining light because it is additive not mixed. All colors of light mixed together become white, unlike paint. Carrara does have a limitation with the light cone. The light cone is different from the light itself, it will go through transparent objects, but will not change color. If you want shader aspects to be affected by the translucency, then you must put them in the shader channel. Put color or bmp or whatever in the translucency channel and the light will be affected by it. You can also put a color in the transparency channel. So the light in Carrara is blended with shaders when you tell it to do so. The light cone is more of an after effect and is not affected as far as color, but it will create 3D shadows through shaders with alpha channels. I am posting an example showing several different effects, it may be a bit confusing, but does show what I am describing. So Carrara can do most of what you want, but the visible light cone has room for advancement.

[LoneGunman]

Light cone is non-phisical effect (real light cones are impossible without interaction with atmosferic particles which are air, dust,fog etc)

Bulb light should create the same effect if enclosed in sphere with little hole in it, but that is not the case in Carrara (that's why Bryce 5 is so slow, it really calculates it all, ). Rendering such effects would slow down rendering engine to the crawl, it seams, I'm sure that TrueSpace is using some kind of trick too, and if you explore it enough, it's gonna show some limitations

Sure, it should be requested as a feature, as all lights should be able to be rendered as volumetric, regardless of shape, DustParticles object should be introduced as well (Cinema4D has them)

[Naomi]

I know you are asking about light cones, and it's true they don't interact the way you would like (wish they did - but the rendering time might be prohibitive).

But translucency works great with other types of lights. Several of us did the Eovia tutorial for tranlucency creating lamps. Here's an example I did. http://ph.groups.yahoo.com/group/Car...8?b=12&m=f&o=0
It uses a regular bulb. But notice that all the colors of the lamp are showing on the ground.

[medeamajic]

arcady,

It is good to test out Carrara to see if it will work the way you would like with lights. I imagine Carrara 6 will have better lighting effects thanks to your post.

[arcady]

medeamajic:

Yes, the purpose of this post is to request the features I want to see.

Not to complain about what is lacking. In the bugs thread I was told it is not a bug, so that means if it is not working the way I desire I -should- post here and try to describe what it is I desire and request it for a future version.


naomi: A renderer with 'ray traced lights' will do what I'm seeking, and while some do, some do not seem to have prohibitive rendering times.
Here I am wondering if Bryce is ray traced and capable. I've only used it in three of my final works, and none of them tested this, but they were all VERY SLOW renders comparred to Vue. Vue is comparable in rendering time Carrara, but minus these light effects I do agree that Carrara renders look 'cleaner'. So it is possible, and desireable. It would allow for the other major features of Carrara's renderer to not be dimished by this issue - and to thus allow it to be fully competitive with other renderers in the same $ price and CPU-needs range. If nothing else, it might be a nice thing to be able to select, for those images where it will matter.


Patrick: could you post your .car file so I could look at it? If everything I desire -actually is possible- then it won't be a feature I am asking for, but a tutorial.

[LoneGunman]

Originally Posted by arcady

...
Here I am wondering if Bryce is ray traced and capable...

I actually used Bryce 5 more then 1000 times, and I can tell you one thing, quality of raytracing is actually still better than people want to admit, but a big downside is high render times (adding real caustics, global ilumination and ambient occlusion to such accurate rendering engine would make rendering times almost unbeliveable). Modern rendering engines use lot of tricks and workarounds to approximate certain effects with more or less success...

Obviously volumetric lights in Carrara need to be reworked, not that I use them a lot, but some people do

Here is Bryce5 sample render (took poor old B5 20 minutes, oh well )

[McHannemann]

Yes, this feature should be implemented,
the best what I got so far is attached,

Regards,

Thor

[Piem]

The first requested feature is YET implemented. as Patrick told it
Just put the same color (at least ..you can combine any color channel with any operation( multiply with high value or grayscale or anything.. in exemple) in the translucy channel and do not forgot to add transparency and to activated transparency in the render ) .
cheers sorry for the very poor and bad image

[arcady]

Using the translucency simulated-work-around to lighting, how would you deal with three lights of different colors shining on a glass object of multiple colors (stained glass) from different angles, and inside that object is a second 'stained glass object' of a different colors, angles, and shapes than the first?

Thus they overlap on where the light exits in part, but not in whole. The exact blending of the light will vary 'photon by photon' and as far as I can tell this can only be done with actual ray tracing of the 'light rays' and the light being changed by everything it impacts - both objects and other lights.

[Piem]

Is it a test Arcady ?
I know that my previous post was an overlapping answer
.but..to this new one i could give answers you know.
I like chalenges .
It about midnight here ,I must think to my bed.. but I 'll get a try

[medeamajic]

arcady,

I do not use lights as much as you but I do use glass and chrome. I would like to think that what you want to do could be done easily in Carrara. It sounds like you will need to do things different from Bryce or Vue. I do agree it should work the way you want by default. I guess we will have to play around with the shader tree to master it. Perhaps Eovia will place some tutorials on lighting and shading of glass objects with multiple lights.

[andywright]

Originally Posted by medeamajic

arcady,

I do not use lights as much as you but I do use glass and chrome. I would like to think that what you want to do could be done easily in Carrara. It sounds like you will need to do things different from Bryce or Vue. I do agree it should work the way you want by default. I guess we will have to play around with the shader tree to master it. Perhaps Eovia will place some tutorials on lighting and shading of glass objects with multiple lights.

This is a good suggestion.

The shader tree is daunting for a new user to say the least, and I am aware that any improvements i might ask for may already be buried in there waiting to be found. The one thing that is clear is that great results are possible with it once you get the hang of the options......

[tonytrout]

Interesting ... discussion

This may or may not be of benefit to anybody but I did some test renders for my own reference as I have wanted to know what the effect of moving some of the shader and rendering options would do anyway , and made up a sheet for reference. I have attached some pics of the test renders

I set up 4 colored spotlights (green, red, yellow and white) through a red coloured plane and onto another default shaded plane, and varied the render options. A red colour was placed in the colour channel, and/or in the transparency shader channel and/or in the translucency channel. In hindsight I should have overlapped the spotlights but 48 renders later I need to do something a bit more creative. In some of the options the red colour washes through from the HDRI lighting, also turning the 'casts shadows' option on and off on the red plane has an effect. The green spotlight doest behave the same as the other colours through the red pane perhaps someone could tell me why, I assume because it is some sort of additive effect between the two colours.

Let me know if this is of any use or a load of old bargswoddle.