|
|
Topic: Glass Detail: I'm on the edge here ;)
posted by BADBOYFXP
archived on 1.5.2002
Why is the vray glass so dark on the edges? The brazil glass looks better here i think.
Both images have nearly same rendertime.
Follow-ups
A: Because the rays bounce inside the glass, without ever going out. I think in this case Brazil assumes the result is the same as the environment color. VRay simply assumes black result.
Q: but environment color is black for both scenes :)
looks like brazil has a more clever way to handle this.
will you change this in future versions?
or can you give me a tip how to achive a better result with vray?
Comment: In Brazil, have you set the "Sky Light" color under "Luma Server Params" to black also?
Comment: As of VRay 1.09.02v the material has added the exit color option.
Q: donīt use skylight or GI. just a simple brazil glass material.
the skylight settings have no influence.
but i was wrong with my first comment. :(
the environment color is set to black, but i donīt notice that i checked the map option, so in fact the environment color is a gradient map.
when i change the environment color to black the BRAZIL image looks similiar to the VRAY image (so Vladimir Koylazov is right :)
but how can i achieve the same look with vray?
the environment color has no influence on the vray rendering.
A: In the VRayMap, the parameter would be "Exit Color". I'm not positive what it is in The VRay Material, but I could imagine that it's similar.
Q: 985.10 in reply to 985.9
i tried a vraymap in the reflect and refract slots of the vray material.
but now the rendering is much (and i mean MUCH) slower.
and the material looks not like glas anymore.
i use the default settings for refract- and reflect vraymap and only change the exit color.
btw: how about disabling the options you donīt need in the vraymap?
i mean, you can choose REFLECT and REFRACT in the vraymap but you are still able to make settings for both options.
A: This is not how it works - no wonder it was slow and not glassy looking...
The VRay map returns a raytraced reflection or refraction. This is varied in intensity according to the VRay map's intensity map.
The VRay material knows how to raytrace, it doesn't need to use maps for it to work.
In the VRay material, the Reflection map does *not* return raytraced rays like the VRay map. Here, instead of generating reflections, it acts as a *multiplier* an intensity control. So you might put a falloff/fresnel map here if you wanted fresnel reflections and they weren't supported by the material, or a bitmap to control how shiny your object is.
When you put a VRay material, which raytraces the scene to see what's around it, in a reflection/refraction slot in the VRay *map*, which controls reflection/refraction *intensity*, what you are doing is getting the material to:
1) Trace rays out into the scene
2) Trace rays out into the scene again
3) Use second set of traced rays to control intensity of first set
Which is kinda weird, makes VRay trace a lot more rays, and looks unrealistic/strange.
So, despite similar names, the way reflection maps work in the VRay material and map are very different. If you want controls available only in the map, you must build a material based on the *standard* material, with a VRay map in its reflection slot with the right parameters and all the energy balancing stuff.
Q: i notice my error yesterday but im still not able to get a result similiar to brazils output.
now i use the vraymap material in the refract and reflection slot of a standard material (EXIT COLOR is set to light grey).
the rendering is still much slower then with the vraymat material and looks ugly.
nothing change on this grey edges when i use better rendering settings.
A: Part of the ugliness you are getting from the map may be connected to falloffs - not only should you have a falloff in your reflect, you need on in your refract too, with the colours reversed.
An exit colour of light grey is probably not an improvement - to get a good glassy effect, you really need contrast, which comes from things like gradients but not a solid gray. If anything, putting solid grey may make it look worse - maybe try a dark grey.
> print this entry
|
 |
|
|
