sprite node ( not sure to like it)

[vbk!!!]

yo,

Sprite node allows to put some sprtiet shader to particle. It's great but ...

The Scale of the sprite is control by the Sprite node and I am not sure to like it.

I would ike to be able to change the size of my sprite with my shader instead of Sprite Pop

Is it possible ?

Thanks for your help

[old school]

No. By the time the shader is called in Mantra, the geometry has already been constructed.

You can control the size of the sprite using an Attribute Create SOP after the particle system.

Here are the values that you need to change:

Name: spritescale

Size: 3

Value: 0.8 0.8 0 0

where you can manipulate the first two values to control the x and y size of the sprite.

The key is to mmb on the popnet SOP and see that there is a vector attribute called spritescale created by the Sprite POP. All attributes are fair game to modify them after they are created.

[TheAdmira1]

Doing it in the sprite POP gives you a lot of control over the size via expression though... you are able to use the life, id, point number, age, sprite size, rotation, and offset... in the example i uploaded im only using the basic dust sprite shader, but using the color POP to set my color, and alpha which controls the color and opacity in the shader... hope this helps!

-Glenn

SpriteTestOdF.hip

[anim]

I would ike to be able to change the size of my sprite with my shader instead of Sprite Pop

Is it possible ?

i am not sure what benefit would that have

if you want to change the spritescale after POPs have been cached to disk and read back, you can do that in SOPs easily

but if you need, yes, it is possible to do it in shader

set your spritescale to maximum desired size of the sprites

then you can just change uvs in the surface shader to vary the scale per particle

the easy method for that is

UVcoords VOP -> Transform Matrix VOP (pivot set to 0.5 0.5) -> rescaled uvs, drive whatever sprite texture you want with them

UVposition may work too, maybe it's better if you need s,t as input values for your texture

just make sure the opacity is set right for your sprite to make everything outside the uv range transparent