Particle Sprites Problem

[Visual Cortex Lab]

Hey guys,

I'm trying to sort out this problem... I'm playing with mantra sprites and i did a simple VOP smoke shader for it ... but I've found a problem.

guess the picture talks itself.. the problem is when sprites goes across the floor..

any advices ?

thanks in advance.

Edit:

to avoid opening another thread I post here a second problem I have with this...

I'd like to have a bit more "depth" of the smoke.. and to archieve this.. I'm using now 3 point lights one of which casts shadows, and which are R, G, and B colored.. in the above picture you see lot green influence.. and a little bit of blue.. but I'd need much more "bumpiness" from those sprites..

I tried by attaching the output of my "noise" color to the "N" output.. but this doenst seems to help too much .. i'd appreciate any hint on this as well.

thanks

[hoknamahn]

[one' date=Aug 11 2006, 05:45 AM' post='29947]

Hey guys,

I'm trying to sort out this problem... I'm playing with mantra sprites and i did a simple VOP smoke shader for it ... but I've found a problem.

guess the picture talks itself.. the problem is when sprites goes across the floor..

any advices ?

thanks in advance.

Edit:

to avoid opening another thread I post here a second problem I have with this...

I'd like to have a bit more "depth" of the smoke.. and to archieve this.. I'm using now 3 point lights one of which casts shadows, and which are R, G, and B colored.. in the above picture you see lot green influence.. and a little bit of blue.. but I'd need much more "bumpiness" from those sprites..

I tried by attaching the output of my "noise" color to the "N" output.. but this doenst seems to help too much .. i'd appreciate any hint on this as well.

thanks

1. You can calculate an intersection mask (between sprite and floor) in composer and use it to blur sprites.

2. Use a texture for bump. Something like circular ramp.

[doc]

[one' date=Aug 11 2006, 06:45 AM' post='29947]

Hey guys,

I'm trying to sort out this problem... I'm playing with mantra sprites and i did a simple VOP smoke shader for it ... but I've found a problem.

guess the picture talks itself.. the problem is when sprites goes across the floor..

any advices ?

Are the sprites being instanced or are you using a copy sop? If you're using the copy sop you can always use attribute transfer to transfer an attribute from the ground plane to your sprites. You can use this attribute to control the alpha of your sprites. Mind you this would mean that you'd have to subdivide you sprite in order to get the right amount of detail.

What would be even better is if you scattered points across your ground plane saved it as a .tbf and used the point cloud function to test for proximity in your sprite's surface shader. This way you wouldn't have to subdivide your geometry at all. This would work with instancing as well.

let me know if you have any questions

Luca

[Visual Cortex Lab]

damn my rss reader didnt noticed me about those two answers...

btw..

those are just sprites.. nothing instanciated nor copied.. those are particles coming out from a GEO that renders as procedural sprites.

1. You can calculate an intersection mask (between sprite and floor) in composer and use it to blur sprites.

2. Use a texture for bump. Something like circular ramp.

2. you mean I need a "bump along normal" vop before connecting to "N" output?

another question ... Mantra is taking quite long time when many sprites are overlapping (low Y camera.. watching the whole smoke sprites near the floor)... is there a way to optimize this?

cheers

[Visual Cortex Lab]

1. You can calculate an intersection mask (between sprite and floor) in composer and use it to blur sprites.

2. Use a texture for bump. Something like circular ramp.

1. i'll investigate on this.. I'm also planning to scale down particles ccordingly to location (near groud f.e.) to make 'em less "cutted"

2. could you please be more explicit on that?.. what in a simple example i'd like to see.. is:

let's say all my sprites have a circular ramp on 'em (with Of) so that they render "like" spheres... i'd like to have highlights (and shadowing which is what I'm actually looking for ) accordingly to the value of the color of the sprite itself.. like a texture projected on a grid.. for bump as you say.. but apparently this doesnt happens in my sprites.. i have no "local" bump .. i just have the whole sprite more or less rought... (which happens as well just with specular lighting types.. while I want shadows.. and i'm using a lamber shader, smoke.. )

hope this is not too much confused .. its a bit late here.. and i must admit i'm having no life at all lately..

cheers

[hoknamahn]

Hey som][one.

I mean this http://www.cgtalk.ru/master/houdini/imask/

Intersection mask allows you to blur the edge of intersection between sprite and floor. I'm not sure what are you looking for but I guess it can help.

you mean I need a "bump along normal" vop before connecting to "N" output

Displacement Along Normal VOP. Yep. I'm sure you need to play with a sprite normals to get the properly effect (good lighting).

Mantra is taking quite long time when many sprites are overlapping (low Y camera.. watching the whole smoke sprites near the floor)... is there a way to optimize this?

The ways to optimize it are disabling of opacity (or increasing of opacity level in your shader and decreasing of Opacity Limit parameter in Mantra ROP). And shadows. They can increase the time of render.

[Visual Cortex Lab]

hoknamahn .. the links seems interesting ... sad I dont understand a word :D

edit: oh well... everything is clear enought from images ... I'm definetly going to give a try .. thanks a lot

[hoknamahn]

sad I dont understand a word

Hehehe... Guys from "Padonki movement" would tell in your case "learn Albanian". But that is not Albanian and I don't suggest you to study anything.

It's sad that HScript and VEX are not standard languages for dialogue of people.

[Jason]

[one' date=Aug 11 2006, 03:30 PM' post='29972]

another question ... Mantra is taking quite long time when many sprites are overlapping (low Y camera.. watching the whole smoke sprites near the floor)... is there a way to optimize this?

I thought I remembered seeing a small optimization for rendering multiple overlapping transparent planes go into the 8.1 DevelopmentJournals but I can't find it. Anyway, try the latest cut of 8.1 and perhaps it'll be a smidge faster?

[Visual Cortex Lab]

using 8.1.865 atm ... and I tried also Opacity Limit ... but that makes the result really bad ...

maybe there's some trick doable in VOP ?...

I'll post a test result later...

[hoknamahn]

The result of the opacity limit is dependent on your requirements and task. So sometimes it is very usable but sometimes not. I think you haven't a choice. But you always can write your own OpenGL renderer for sprites That can really accelerate your renders.

[Visual Cortex Lab]

ehehe i wish i was able to write my own OpenGl renderer

[Andrew]

You can add color to your particles , brighter on the top and darker on the button.

It will be absolute fake but it will look like your sprite volume have absorbed illumination

which makes it look like it cast shadows on its self.

It works 98% of the cases.

Cheers.

Andrew