Help with Glass shader

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Old 11 November 2012   #1
Help with Glass shader

Hello all,

I am trying to make a glass shader with the help of the Blinn Material.

I have 2 doubts and it is really driving me crazy.

1. I have a lamp and I have placed a point light inside the lamp. For the lamp glass, I am using the Blinn Material with refractions and I am using a ramp for transparency to get a Fresnel effect but the ramp now is blocking all the light. What should I do so the light can pass through?

2. I want to make my lamp look a little weathered so that it looks like it has cracks and dust on it. What can I do to add that effect without using a layered shader. Is there anything I can do.

Appreciate your help. Thanks a lot.

Sid
 
Old 11 November 2012   #2
Are you using mental ray to render, or another rendering program?

Are you using Maya?
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Old 11 November 2012   #3
Yup I am using maya and mental ray.
 
Old 11 November 2012   #4
If you're using mental ray, you should be using the mental ray shaders instead of the Maya native shaders. The mia_material_x, specifically. There are many reasons to use this shader - automatic Fresnel (in the BRDF rollout), energy-conserving behavior, and a ton of other features which make the Maya native shaders deprecated. On top of the features though - the mia_mat_x can often render faster too!

You can also link in a Light_Surface shader to your glass to simulate a light bulb or lamp shade. This would go in the Additional Color slot of your mia_mat_x.

For dust, scratches, etc. use a bump map or attach your texture to the reflections channel, or to the diffuse channel. Many, many ways to do this with the mia_mat_x.
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1541 Floppy Drive


"Like stone we battle the wind... Beat down and strangle the rains..."
 
Old 11 November 2012   #5
I'm not a Maya user but if you have problems lighting the scene... try making two lights, one excluding the light from the lamp geometry to light the scene and another including only the lamp.... and definitely use the mia_material as InfernalDarkness said it will make things a lot easier to achieve.
 
Old 11 November 2012   #6
I see what you're getting at Vital, but this isn't physically accurate and will only hurt the lighting as you attempt to approach realism. The best way to approach realistic lighting is with realistic lights! The light_surface should be sufficient to simulate the bulb, with an area light inside for the actual light of course.

When using mental ray for realistic lighting, all your lights should be area lights. The reason for this is that area lights have surface area, unlike point or spot or directional lights which have none. Lights without surface area rely on "specularity" which is a workaround ad-hoc method of simulating surface reflections.

With the mia_material_x, there's no need for fake specularity. Reflections are physically accurate and energy-conserving, so you don't need the old style lights anymore.
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"Like stone we battle the wind... Beat down and strangle the rains..."
 
Old 11 November 2012   #7
Originally Posted by InfernalDarkness: I see what you're getting at Vital, but this isn't physically accurate and will only hurt the lighting as you attempt to approach realism. The best way to approach realistic lighting is with realistic lights! The light_surface should be sufficient to simulate the bulb, with an area light inside for the actual light of course.

When using mental ray for realistic lighting, all your lights should be area lights. The reason for this is that area lights have surface area, unlike point or spot or directional lights which have none. Lights without surface area rely on "specularity" which is a workaround ad-hoc method of simulating surface reflections.

With the mia_material_x, there's no need for fake specularity. Reflections are physically accurate and energy-conserving, so you don't need the old style lights anymore.


100% indisputable. old habits die hard, it seems. Alot of people still seem to depend on the old legacy-hacks when using physically-based renderers like MR.
 
Old 11 November 2012   #8
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