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Tindytim

Heavy use of Parallax mapping on Low Poly Models?

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Tindytim    122
I would first of all like to say I am not a Programmer (at least not a good one). I am learning. However I am a 3D Modeler, and this question has had me thinking. Rather than had multi LODs for a single Model, why not use the model used for physics, then apply a parallax map to it? Would that save processing power, versus the conventional low poly for physics and high poly for render? Am I wrong in assuming that there is a mesh for physics (on that resembles the higher poly mesh) rather than a collection of shapes for the various body parts along the skeleton? I'm sorry if this is the wrong section.

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OrangyTang    1298
Quote:
Original post by Tindytim
Am I wrong in assuming that there is a mesh for physics (on that resembles the higher poly mesh) rather than a collection of shapes for the various body parts along the skeleton?

Depends on the game and what it's being used for. Having a low poly collision mesh is certainly one way of going about it, however it might just be a collection of primative shapes (spheres, capsules, etc.) attached to the skeleton and therefore not really suitable for rendering.

Personally I prefer the second approach, as the last thing you want is for an artist to change the model of a character and suddenly break all of your carefully weighted gameplay because they're suddenly much easier/harder to hit now.

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Tindytim    122
Quote:
Original post by OrangyTang
Personally I prefer the second approach, as the last thing you want is for an artist to change the model of a character and suddenly break all of your carefully weighted gameplay because they're suddenly much easier/harder to hit now.


How would Parallax mapping affect the collision detection, or weight painting (or something similar?)?

And would it still be less processor intensive to use a low poly model (not necessarily the one used of Collision detection) and apply maps to it? possibly changing to lower detail maps for the LOD?

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Using parallax mapping with a very low poly model brings a couple of problems of its own.
Simple parallax mapping is only a coarse approximation which only really looks good on relatively low frequency data. Parallax occlusion mapping or relief mapping or any other ray-marching technique is better, but still does not display correct silhouettes, at least not without some pain and significant shader overhead. The overhead for correct self-shadowing is not neglegible, either.
And then of course, there's aliasing, texture bandwidth, uh... and a few other issues.

All in all, parallax mapping is a great "plus", and the ray marching variants are an even greater "plus", but I don't think they're suitable as a complete drop-in replacement for geometry.
Just imagine you have to do ray marching for 4 shadow maps in addition to your normal rendering passes.

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Sneftel    1788
What the physics system wants is not the same as what the graphics system wants. For the graphics system, polycount is everything. For the physics system, what really counts is being able to easily decompose the object into convex subobjects. This means removing concavities (even large ones) and not worrying so much about high-poly rounded edges. Basically, although both systems want low-poly objects, the best particular low-poly objects are different for the two.

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Sc4Freak    643
I am of the opinion that in most cases, parallax occlusion mapping isn't worth it. Unless you need to represent some incredibly high frequency data, it would probably be cheaper (in terms of both performance and effort) to just use more polygons. Parallax occlusion mapping is incredibly shader-heavy, and is hardly free.

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Krohm    5031
I agree completely. In fact, I still don't see why so much people is screaming for it. Personally, I'm pretty fine with offset-limited parallax and a few extra triangles.

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