puma.snyder Posted January 11, 2004 Share Posted January 11, 2004 I want to construct an illuminance loop which does not consider the position of the lights in the scene, so that the whole surface glows only based on the intensity of the light. A renderman user told me he would use illuminance( position [, nsamples] ) instead of illuminance( position, axis, angle [, nsamples] ) In vex there is only the equivalent to the second loop, so how can I build the first one in vex? or do I just have to increase the angle parameter? Thanks again Achim Quote Link to comment Share on other sites More sharing options...
Mario Marengo Posted January 12, 2004 Share Posted January 12, 2004 Hi puma, Yes; just increase the angle. The difference between prman and mantra in this case is that, when given just the single parameter 'P', prman defaults to [axis = N, and angle = PI], whereas mantra defaults to [axis = N, angle = PI/2]. Mantra has the more usual hemisphere as default. To sample lights from the whole sphere then: #include <math.h>surface MySurf(...) { Quote Link to comment Share on other sites More sharing options...
puma.snyder Posted January 12, 2004 Author Share Posted January 12, 2004 thanks Mario , that makes perfect sense. (the bit about "glows only based on the intensity of the light" is just a short part copied from "Shading a Coral reef" from Siggraph 03) I'm quite certain that there's no illuminance construct in prman with that signature I have no experience with prman and just copied those from here https://renderman.pixar.com/products/rispec...tml#Illuminance Thanks again Achim Quote Link to comment Share on other sites More sharing options...
Mario Marengo Posted January 12, 2004 Share Posted January 12, 2004 Hi Achim, I have no experience with prman and just copied those from herehttps://renderman.pixar.com/products/rispec...tml#Illuminance Ah, I see... that's from the 3.1 spec (published in '89). It's certainly not the way it's implemented currently (or for quite some time). It's very interesting to see that, though; I guess they were trying to generalize the concept (in the spec) to account for "future" GI, even back then. That signature is a lot closer to the modern "gather" construct, wich is similar in spirit, except it *does* sample irradiance and so has a [,samples] param... fun prman trivia Cheers. Quote Link to comment Share on other sites More sharing options...
puma.snyder Posted January 12, 2004 Author Share Posted January 12, 2004 thanks for the explanation Mario. got it working now Quote Link to comment Share on other sites More sharing options...
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