Integrating 3D models with photography
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# 1 08-12-2002 , 09:19 AM
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mental ray stories -Final Gathering-

I plan to finally dive into mental ray and get a little wiser.

Please contribute with your godlike knowledge of mentalray user added image

FIRST SOME ISSUES:

mentalray Beta doesnt seem to support the render-region function in maya. Which means you have to (if I'm not wrong) render whole images, every time you render with mentalray.

SO FAR... (About Final Gathering)

I have found out that you can use a materials "incandesence attribute" to act as a lightsource. BUT You need to create a light, else the default lights appear and wash the scene with light. Set the intensity of the created light to "0". You need not turn on any photon emitting with final gathering alone (it seems)

ABOUT THE RADIUS SETTING...

-I have read at several places that the MAX radius should be like 5-10 % of your scene's size in maya units.
-MIN radius should be like 10% of MAX radius. Im not sure, but it was also said that the min radius should be made smaller to take into account the smaller objects in the scene. But I dont know (at this time) what the differences will be, if MIN radius is too big for your smaller objects.

The pic below shows a final gathering rendering with one material, having some incandesence. Im sure I can figure out how to make the "light source" dissappear, but I not sure how at this point.

# 2 08-12-2002 , 09:27 AM
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mental ray stories -Final Gathering- 2

The incadensence value was set to max.

# 3 08-12-2002 , 09:31 AM
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mental ray stories -Final Gathering- 3

The object (with incandesence material) acting as a light source was scaled bigger.

# 4 08-12-2002 , 10:03 AM
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mental ray stories -Final Gathering- 4

The initial light source was removed. A new poly sphere was created and scaled up, until my scene and the perspective camera were inside the sphere.
The poly-sphere is fully enclosing.
Incandesence is still set to max.


Last edited by undseth; 08-12-2002 at 10:06 AM.
# 5 08-12-2002 , 10:15 AM
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mental ray stories -Final Gathering- 5

Same as previous but the poly-sphere was exchanged for a 180 degree nurbs sphere.

I can't see any major change here.

edit:
hmm the diffused light seem a little brighter in the last rendering. And the light seems to be more intense from the top, and not so bright from the sides as in the former rendering.


Last edited by undseth; 08-12-2002 at 10:41 AM.
# 6 08-12-2002 , 10:28 AM
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mental ray stories -Final Gathering- 6

Same as previous, but the incandesence is set to 50%.

# 7 08-12-2002 , 10:38 AM
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mental ray stories -Final Gathering- 7

Same as previous, but the incandesence is set to 25 %.

# 8 08-12-2002 , 10:54 AM
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mental ray stories -Final Gathering- 8

I have now removed the point light (whos intensity was set to "0") and added a directional light.

Directional light intensity is set to "1".
Color: slightly yellow.
Shadows are raytraced.

? It seem that there are no shadows cast from the dir-light.

# 9 08-12-2002 , 11:11 AM
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mental ray stories -Final Gathering- 9

I hid the sphere, and the shadows did appear after that. Why is this?

Edit: Solution See next post!


Last edited by undseth; 08-12-2002 at 11:49 AM.
# 10 08-12-2002 , 11:51 AM
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mental ray stories -Final Gathering- 10

Ah, I checked out some of the attributes to the nurbs sphere;

Check out BOTH of these:

CAST SHADOWS
RECIEVE SHADOWS

Dir-light intensity was set to 4.
Nurbs sphere, incandesence was set to 25%.

! If you want to make the sphere non-present in your rendering, check out also the;

PRIMARY VISIBILITY

user added image Now I'm getting somewhere.


Last edited by undseth; 08-12-2002 at 12:19 PM.
# 11 08-12-2002 , 01:13 PM
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mental ray stories -Final Gathering- 11

Looks nice I think; I'll start with this pic, and do some changes to the FG settings and not the lights.

1000 FG rays
Min rad: 0.1
Max rad: 1.0

Min samples: 0
Max samples: 2

# 12 08-12-2002 , 01:26 PM
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mental ray stories -Final Gathering- 12

FG rays: 200

Comment: The pic has clearly gotten more grainy.

# 13 08-12-2002 , 02:21 PM
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wow, that is a great thread, keep em coming. :banana: i need learn some more about mr.

user added image

# 14 08-12-2002 , 02:43 PM
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mental ray stories -Final Gathering- 13

This pic:

FG rays = 4000 (!)

This setting is quite a time waste if you are just fooling around. I'll go back to 200 and try some light angle with the raytrace dir-light!

# 15 08-12-2002 , 03:04 PM
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mental ray stories -Final Gathering- 14

FG rays set back to 200
The directional light has the light-angle set to 5 degrees with 1 shadow ray.

Thus we see the shadows as quite grainy.

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