H11, Mantra and Curve Rendering Wierdness

[barad_dur]

Hello all,

I was running through cmiVFX's L-Systems 2 video and came across an issue. The curve shader that David set up doesn't work in H11 . . . well, it KINDA doesn't work . . . Let me illustrate:

I have an L-system that is set to skeleton and is running through a Material SOP that points to the curve shader that David built. When I render from the Mantra1 node I get:

However, if I go to the IPR (render View tab) I get this:

The IPR render is generated using the same Mantra node as the actual Mantra render which generates nothing but black.

I have attached the .hip. cmiVFX_curveRendering.hipnc

If anyone can give me a heads up as to why IPR renders this fine but the Mantra node itself doesn't I'd be appreciative. Thank you.

David

[sanostol]

the problem is the shader. either You use another shader, the bumpmap shader seems not to work with micropolygon, or You use the raytracing rendering engine, because here it works (don't ask me why, I'm curious, too ).

But You can also just check the "shade curve as surface" flag on the object level.

Martin

[ikarus]

just a heads up: if you have preview turned on in IPR render view it sets your render to raytraced even if ur set to micropolygon in mantra node

[barad_dur]

just a heads up: if you have preview turned on in IPR render view it sets your render to raytraced even if ur set to micropolygon in mantra node

Well that would explain quite a bit including why, when unchecked, preview was giving me bupkiss. Thanks ikarus

[barad_dur]

the problem is the shader. either You use another shader, the bumpmap shader seems not to work with micropolygon, or You use the raytracing rendering engine, because here it works (don't ask me why, I'm curious, too ).

But You can also just check the "shade curve as surface" flag on the object level.

Martin

Sanostol,

Thank you for that info about the "shade curves as surfaces" at object level (it's in the Dicing tab for those who want to know). The only problem is that it renders curves as ribbons. The "curve" shader that David built defines a curve as a "half-hemisphere" who's surface always faces the camera so you get the illusion that the curve is a tube (hence the half hemisphere definition) and not just a line.

The reason this seems important for me to get working is that I would love to have multiple, high generation, trees in a scene. It would seem to me that if I just switch on "Tube" in the L-System type then I am heading into "geometry heavy" territory especialy after copying the L-sys to a scatter with 500 points or so. It would seem important to have a shader that could fake that. The utility just cannot be dismissed.

For instance, if I wanted to greeble the side of a cube to make it look "Borg-ish", A La Star Trek, I could lay down a $%!t load of lines and run it into a polywire and crank up the columns and rows. Or I could not have to deal at all with all that extra geometry and just tell Mantra, "Hey, dude, when you see a line just make it look like a tube". It may just be that I have no choice but to stay in raytracing for this.

Anyway, many thanks.

[Macha]

Hi there David, I attached you a file that shows you how to orient a line and how to shade it like a tube by ramping the s or t coordinates.

It is rough but perhaps it gives you a starting point. With a little rewiring you should be able to plug it into a bump or displace.

bump.hip

Edited December 14, 2010 by Macha

[barad_dur]

Hi there David, I attached you a file that shows you how to orient a line and how to shade it like a tube by ramping the s or t coordinates.

It is rough but perhaps it gives you a starting point. With a little rewiring you should be able to plug it into a bump or displace.

Thank you Macha. I tried out the hip file and it has confirmed my suspicion that micropolygon rendering is not going to cut doing this type of thing: this hip only renders correctly in raytracing. It seems that raytracing is the only way to get this type of thing done.

I guess the the thing I have to wonder is is if micropolygon rendering actually has to have a real primitive to work from. I don't think that a curve could be considered a primitive but I might be wrong. Anyone from SFX here have an idea about what is going on here? I'd really like to know more about this issue and it's suggestion about rendering theory.

[Owl]

Thank you Macha. I tried out the hip file and it has confirmed my suspicion that micropolygon rendering is not going to cut doing this type of thing: this hip only renders correctly in raytracing. It seems that raytracing is the only way to get this type of thing done.

I guess the the thing I have to wonder is is if micropolygon rendering actually has to have a real primitive to work from. I don't think that a curve could be considered a primitive but I might be wrong. Anyone from SFX here have an idea about what is going on here? I'd really like to know more about this issue and it's suggestion about rendering theory.

Hi,

it does work with micropolygon rendering you just need to check "shade curve as surface"

can you show what's wrong with Macha's hip in micropolygon rendering?

[maxgrip]

Macha could you provide hip that will work on H10? (shader)

[barad_dur]

Hi,

it does work with micropolygon rendering you just need to check "shade curve as surface"

can you show what's wrong with Macha's hip in micropolygon rendering?

Owl,

I certainly can! You see, I'm just not that bright and didn't think to switch on shade curve as surface. Of course, once I did the thing rendered exactly as advertised. While embarrasing one thing is for sure: this type of "learning while making dumb mistakes" makes one never forget a particular thing ever again. So there is a certain utility in that I suppose.