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Mantra+Siggraph 2002 Course 16=


AndrewVK

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Unfortunately, VEX does not have the common space (real "World" space),

that is why for the correct calculation of the ambient illumination it is

necessary to create a "null" object, and for the objects using the shader,

to switch the Shader Space (Shading page) from "This Object" to "null".

FakeDiffuse.zip

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Unfortunately, VEX does not have the common space (real "World" space),

that is why for the correct calculation of the ambient illumination it is

necessary to create a "null" object, and for the objects using the shader,

to switch the Shader Space (Shading page) from "This Object" to "null".

I think VEX has real "World" Space. Or maybe I don't know what I'm talking about. :unsure:

Extract from the VEX docs, shading.html:

In all VEX contexts, global variables are in "world" space. In the mantra renderer, this space is defined with the camera at the origin pointing down the positive Z axis. Each shader has a local "object" space associated with it. This is the space which defined as the object at the origin of the space. Displacement, Surface and Light shaders also have a special "NDC" space associated with them.

You can find Transform functions under the Transform Spaces section of the above document.

I hope the above helps!

Cheers!

steven

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aaargh...nope...VEX doesn't...and to make it more complicated on Rman users, it actually reverses the notation (sorry, Marc (E.) I know there is a reason for this....)

thus in Rman you have World, object, Camera Spaces

in Vex (respectively) it becomes N/A, object, World spaces....

NDC is onither "camera" space with its coordinates "normalized" (ie: the screen runs from 0-1 in both axes, not sure about the Z....pretty handy...)

VEX-World-with the camera at the origin pointing down the positive Z axis

well, this is the definition of Camera space in all other renderers, ultimately it's just a naming convention (and a philosophy), as long as all coordinate systems are available, no matter what the name, I'd be happy ;)

it just requires some mind-bending from Rman people

you can imagine "real" world space to be that null that Andrew created, except it would be iimplemented in VEX, and be available as an option...

just my 2c (from memory :P )

cheers, everyone.

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  • 4 weeks later...

AndrewVK, are you still with that white line problem? You probably know this but anyway...

I was doing some tests myself in softimage and lurking around the web...I think you need some kind of bias for the occlusion calculation, just like when using shadow maps.

I think the problem comes when the point being calculated is occluded by a primitive that passes through it, the rays traced from the point don't hit anything, and so appears as a white point.

Not of much help i know...

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  • 1 month later...
Hmmm...actualy (sometimes) it doesnt work correctly:(

Something wrong with environment sampling.

I have no idea how to fix this :(

Simple blur (without multysampling) works fine...but the result is

more "reflection like".

One idea is you could always pre-convolve (blur) the environment map with HDRShop with a diffuse kernel and just do one env map sample.

Try that out...

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