Light through translucent cube
Author
What I''m trying to achieve is that in my voxel engine, you can see more through one translucent cubes than through two translucent cubes of the same kind, in a realistic way. Also if you look through one cube, you can see more or less through it depending on how the lightray goes through it (e.g. if the ray goes through a corner of the cube for a few centimeters, much less light is absorbed). And I''m not really planning to do refraction.
quote:Original post by sQuid
Not all translucent materials scatter the incident light. Moreover when they do the emitted photons often have longer wavelengths, in the infrared or microwave.
Isn''t this the difference between transparency and translucency?
quote:Dictionary.com
Translucency : Transmitting light but causing sufficient diffusion to prevent perception of distinct images
quote:Sometimes electrons exited by incoming light might jump into a conduction band and no photons are re-emmitted at all. I think this is what happens in tinted glass where metal powders are added to the glass in the manufacturing process.
This is transparency; tinted glass doesn''t blur the image.
Anyway, this all theoretical. Exponential functions will work fine for CG.
Cédric
Lode, what you are trying to do is slightly different then the way you initial stated the problem. Assuming we are working with a point light infinitely far away, all areas of the cube should have the same brightness (as long as the viewing plane is parallel to the edge of cube which is parallel to the light wavefronts). Furthermore, I think what we are talking about is transmittance and absorbtion of light through a medium, which is definitely an exponential process. An object will blurr an image when light coming through the boundary of the medium is diffracted at different angles. I think its much like specular and diffuse reflection off of an object. It also depends upon the internal structure of what you are looking at. If you want the corners to be brighter, than you are going to have to calculate the distance the rays must go through. I would assume that the scattering of light inside is relatively constant (a fair assumption), and then do raytracing, but this is what you don''t want to do. Try posting it on the graphics forum, they probably know more about stuff like this there.
Brendan
Brendan
Author
I''m sorry, I appearantly used the wrong word, I meant transparent instead of translucent! Dumb dumb me. So I got no heavy blur and scattering calculations to do at all 
I think I got my answer pretty much answered now, I''ll try to do it exponential, thanks.
I think I got my answer pretty much answered now, I''ll try to do it exponential, thanks.
quote:Original post by cedricl
Isn''t this the difference between transparency and translucency?
Yes. Good point.
In response to the original post, I think the light that passes through the cube depends on the index of refraction of the material, not the volume of the material, as well as the number of interfaces between the light source and destination. Here''s a general equation for finding the intensity of refracted light at an interface:
Ir = ( (ni - nr) / (ni + nr) )2 Ii
Ir is the intensity of the light refracted from the cube.
Ii is the intensity of the incoming, or incident light.
ni is the refractive index of the material from which the incident light is originating
nr is the refractive index of the material the light is passing into
For your specific problem, I see two interfaces. The first is the air-to-cube interface, and the second is the cube-to-air interface. The refractive index of air is approximately equal to 1. Hypothetically, let''s say that the refractive index of your material is 1.5, an average type of glass. Substituing these values gives:
Ir = ( (ni - nr) / (ni + nr) )2 Ii = ((1 - 1.5)/(1 + 1.5)2 Ii = (0.04)Ii
If 4% of the original light is refracted at the air-to-cube interface, the Law of Conservation of Energy states that this will leave 96% to pass through the cube itself (inside the cube). Solving for the intensity at the cube-to-air interface will also yield 4% refraction. So 96% of the light in the cube will actually pass through. Simple multiplication shows:
(0.96)(0.96)100 = ~91%
Approximately 91% of the original light passes through the cube. So, to make a long story even longer, I''d say that the intensity of the light will still be 50% no matter how long you make the cube. Gotta love physics.
Also note that if you double the thickness of the cube, it''s no longer a cube.
"If people are good only because they fear punishment and hope for reward, then we are a sorry lot indeed." - Albert Einstein
Ir = ( (ni - nr) / (ni + nr) )2 Ii
Ir is the intensity of the light refracted from the cube.
Ii is the intensity of the incoming, or incident light.
ni is the refractive index of the material from which the incident light is originating
nr is the refractive index of the material the light is passing into
For your specific problem, I see two interfaces. The first is the air-to-cube interface, and the second is the cube-to-air interface. The refractive index of air is approximately equal to 1. Hypothetically, let''s say that the refractive index of your material is 1.5, an average type of glass. Substituing these values gives:
Ir = ( (ni - nr) / (ni + nr) )2 Ii = ((1 - 1.5)/(1 + 1.5)2 Ii = (0.04)Ii
If 4% of the original light is refracted at the air-to-cube interface, the Law of Conservation of Energy states that this will leave 96% to pass through the cube itself (inside the cube). Solving for the intensity at the cube-to-air interface will also yield 4% refraction. So 96% of the light in the cube will actually pass through. Simple multiplication shows:
(0.96)(0.96)100 = ~91%
Approximately 91% of the original light passes through the cube. So, to make a long story even longer, I''d say that the intensity of the light will still be 50% no matter how long you make the cube. Gotta love physics.
Also note that if you double the thickness of the cube, it''s no longer a cube.
"If people are good only because they fear punishment and hope for reward, then we are a sorry lot indeed." - Albert Einstein
In a situation such as Lode was talking about with partial transparency, the amount of reflected light (which is what your equation represents) is trivial compared to the amount of absorbed light. And that latter is dependent on the width of the material.
Don''t listen to me. I''ve had too much coffee.
Don''t listen to me. I''ve had too much coffee.
Yes, you''re right. I completely forgot about absorption. Though, assuming my reasoning and computations in my previous post, I still don''t think refraction is anything to scoff at.
"If people are good only because they fear punishment and hope for reward, then we are a sorry lot indeed." - Albert Einstein
"If people are good only because they fear punishment and hope for reward, then we are a sorry lot indeed." - Albert Einstein
Sorry Sneftel and to the coffee-drinking people around (as myself for instance).
I didn''t get that you actually had an exponent I just saw q*w.
Personally I prefer to write in "computer readable" form:
exp(arg) sin(arg) etc
to make formulas readable when no LaTex or similar in in use.
/Ola
I didn''t get that you actually had an exponent I just saw q*w.
Personally I prefer to write in "computer readable" form:
exp(arg) sin(arg) etc
to make formulas readable when no LaTex or similar in in use.
/Ola
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