PDA

View Full Version : Strands Texture Mapping?


hellomojo
06-17-2011, 03:14 PM
Hi there,
Really stuck on this and it's wrecking my head, I know there must be a way....

I'm trying to achieve the trail type effect in the pic attached. I have set it up different ways each becoming
null and void for different reasons. I think it best to use texture maps on ICE -strands. So I just need to be able
to control the mapping on the strands generated.( I need to have once texture repeating down the generated length).

The effect needs to exist in place and not move once generated, texture must not slide with growth of strands.

I know it's to do with attributes access in the render tree, which I'm a bit lost in. I think the dynamic generation of the strands
is causing me problems too...

I would really be grateful for any help...

thks.
Alan.

oddforce
06-17-2011, 04:01 PM
Just an idea, it could it be possible to store strand length in an attribute, and then read this in the render tree to remap the strand uv values.

For strand shape like cylinder it's a little difficult maths-wise because the V values from the outside part go from 0,25 to 0,75 not from 0 to 1 because of the cylinder's caps.

ThE_JacO
06-19-2011, 09:15 AM
If you need the effect to be that of screen space pinning, then making sure that there is no crawling/sliding whatsoever over a curve/surface that changes frame by frame is more work than it's worth, and pretty bloody hard to begin with.

Pre-create your paths and then animate the visibility/transparency over them instead, and you won't have the problem.

hellomojo
06-19-2011, 06:54 PM
Thanks guys.
I have a solution using ICE and strands without the need for texture mapping. Simplification essentially. I will post some grabs once it is complete. It's more the 'Lighttrails effect' and less fire they are after anyway.

ThE_JacO
06-20-2011, 12:53 AM
If you want a more fire like effect without having to pre-gen, you could also consider using more strands, and pushing them through a noise.
If the noise lives in the world space, things will travel through it without adjusting or crawling (provided time is static on it). Consider it if you need something like that and don't want to move towards texturing.

For a decent sampling of the noise's space though you might end up having to use fairly high point counts for the strands.

oddforce
06-20-2011, 03:48 PM
What also might (have) work(ed) here is something like the TrailSpiral scene in the samples folder (it uses the volume shader, particle density apparently works for strands, too... Nice!)

hellomojo
06-20-2011, 04:19 PM
Cool, looked them up there (the sample scenes), close.... but I couldn't afford the render times anyway. So I haven't used a volume particle shader but have achieved similar results... I'm fine tuning etc.
so will post diagrams when done, simple enough really. I'm using motion blur and fractals to give the light wispy effect etc.

hellomojo
06-21-2011, 04:39 PM
Hi there, so RenderTree network attached. I used Generate strand trails for the ICE tree - everything kind of standard. I pinned the particles to the emit location. The motion blur gives them a nice wispy, watery blend fx. This is also helped by mildly affecting the look with a CellScalar. 2 other simple ICE trees were used for subtle smoke and sparks.
So the best of this is that I avoid volume shader rendering etc. so I can get results quickly using the constant shader.

Thanks for the help.

CGTalk Moderation
06-21-2011, 04:39 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.