merging different types of maps

[hitch]

Hi guys

I have been doing some displacement and bump mapping renders both have been coming out quite nicely, thanks to all the info i have found on this forum, But i have hit a brick wall in regards to using both displacement and bump mapping on the one model. when i use vray i usually use a displacement map for the large forms and bump mapping for the little details, gives a nice render at a reasonable time. was hoping to do this in houdini but am struggling a bit. does anyone know of a method for this? or if someone has a link to a thread that would be awesome.

thanks again to all the people who post here, this site is a goldmine for information, esp for people like me who don't physcially know anyone who uses houdini.

[symek]

Hi guys

I have been doing some displacement and bump mapping renders both have been coming out quite nicely, thanks to all the info i have found on this forum, But i have hit a brick wall in regards to using both displacement and bump mapping on the one model. when i use vray i usually use a displacement map for the large forms and bump mapping for the little details, gives a nice render at a reasonable time. was hoping to do this in houdini but am struggling a bit. does anyone know of a method for this? or if someone has a link to a thread that would be awesome.

thanks again to all the people who post here, this site is a goldmine for information, esp for people like me who don't physcially know anyone who uses houdini.

You may check if bump mapping gives you any advantage, since as you know displacement is really fast in Mantra. Anyway, here is an example of mixing bump with disp. As you see it's just a matter of using two displacement along normal VOPs, instead of one.

hth.

skk.

disp+bump.hip.zip

[sam.h]

I don't think bump mapping will be any faster, since it still has to dice the geometry to get the new normal, right? or should bump mapping be done in the surface shader ... hmmm

[symek]

I don't think bump mapping will be any faster, since it still has to dice the geometry to get the new normal, right? or should bump mapping be done in the surface shader ... hmmm

1) bump mapping can be performed the same way in surface shader (with disp. alond normal Vop), and won't be any faster I suppose.

2) I suspect that as long as there is not redicing involved and displacement bound is not changing dramatically, displacement does not introduce additional dicing costs, so dicing happens the same way in both cases. It's just that in displacement case, micropoly corners are moved around, so this takes additional time. What does cost a lot, is raytracing displacement. Maybe this is a reason to use bump mapping as a secondary disp...?

[Jason]

I'd say that if you use a displacement shader at all, you may as well do the fine details in there, unless you're suffering ShadowMap artifacts due to high frequency displacements (and can't fix it with bias, etc). Once you've paid the cost of running a displacement shader, you may as well keep your workflow simple and just do it all in there. You also end up using the same units and you have a single quality control for all of it. (Shading Quality)

IMHO the only time to split it up is if you're using some kind of fancy bump mapping algorithm which might do other analytical antialiasing, or doing some approximation of diffuse response at greater distances. By the latter, I mean take the high freq bump on the wall of an iceberg: up close is it white marked with little blue shadows due to the pertubations of the surface. As you move away from it, the texture filter will return the filtered texel (averaging out the normals to a smoothed normal) and so the diffuse() function is now reflecting based on a new direction, resulting in a luma and color shift. If some of this is done in the surface shader as bump, you at least have the opportunity to counter-act this artifact. In fact, I suppose it would be a good idea to RFE SideFX into returning the effective filter width Mantra used for a particular texture()/bumpmap() call.... and perhaps this could used by a shader writer to help such problems out.

[rd1010]

Displacement shaders are the way to go.. in the material SOP do a tab < mantra displacement < layered displacement and then you can put the different maps layered in there and control the displacement amount for each.. also something to take note of is that you may have to increase the shader quality of your object to get the displacement map to look right... in the main object SOP area click on the object and then go to render < dice (I think.. just doing this off memory) and then you can adjust the shader quality and raytracing quality.