templargfx opened this issue on Nov 04, 2010 · 75 posts
bagginsbill posted Wed, 17 November 2010 at 7:38 AM
The lens trick I posted only works up to a point. If you push it too far, it produces wild distortion.
Schecterman - I can't think of a way to do this with materials in today's Poser. One of the drawbacks of the node system is that we can't make new ones by writing code. So we can only do things by assembling a fixed set of functions.
One of the key missing functions is a node that tells us where the ray is coming from - behind or in front of the polygon. We have the Edge_Blend node that tells us the dot product (cosine of the angle between) the ray and the surface normal, and it should be possible to use that. But, unfortunately, it returns the absolute value of the dot product - it is always a positive number from 0 to 1. If it was -1 to 1 (not the absolute value) then we'd know when we're behind the polygon whenever the dot product is negative. Alas - there is no way to get at the negative values.
I have other uses for such a feature. For example, the phenomenon of total internal reflection (such as produced by a cut diamond) can be correctly simulated only if I know whether I'm doing a reflection from inside or outside the object. If Edge_Blend had a mode where the dot product could be positive or negative, I could do the accurate reflection.
Another example - the ratio of index of refraction passing through a polygon from the "front" is different than from the back. But Poser's Refract node pays no attention to this. If I could read which side I was on, I could make this work correctly by switching the IOR.
Oh well - maybe in Poser 9.
Meanwhile - the real problem isn't a need for funky shader/camera tricks. The real problem is how to see through a nearby obstruction. We need the camera to implement the "hither" feature in rendering instead of just in preview. If it did, you'd just set it. A wall (or windows or hung pictures, etc.) would not be visible to the camera, but would be visible to IDL, reflections, etc.
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)