API

Color Ramps, Blends, and Billboard Mode

Ramp Gradients

Ramp gradients produce a gradient color texture by assigning a color to an index between 0 and 1

To produce a gradient color texture, such as the color bar above, you need the addRampGradient method

particleSystem.addRampGradient(fraction_of_bar, color3);

For this particular color bar you use

particleSystem.addRampGradient(0.0, new BABYLON.Color3(1, 1, 1));
particleSystem.addRampGradient(0.09, new BABYLON.Color3(209/255, 204/255, 15/255));
particleSystem.addRampGradient(0.18, new BABYLON.Color3(221/255, 120/255, 14/255));
particleSystem.addRampGradient(0.28, new BABYLON.Color3(200/255, 43/255, 18/255));
particleSystem.addRampGradient(0.47, new BABYLON.Color3(115/255, 22/255, 15/255));
particleSystem.addRampGradient(0.88, new BABYLON.Color3(14/255, 14/255, 14/255));
particleSystem.addRampGradient(1.0, new BABYLON.Color3(14/255, 14/255, 14/255));

To use them you need to turn them on.

particleSystem.useRampGradients = true;

By default the alpha value of the particle (built from textureAlpha * particleColorAlpha) is used to as the index get the ramp color from the ramp gradient using this formula: finalColor = textureColor * particleColor * rampColor.

Ramp gradient: Ramp Gradient Example

To give you more control you can use a remap function to change the index over time with 

particleSystem.addColorRemapGradient(fraction_of_lifetime_elapsed, minimum_index, maximum_index); //set a range of values for the index at the given time point
particleSystem.addColorRemapGradient(0, 0, 0.1);
particleSystem.addColorRemapGradient(0.2, 0.1, 0.8);
particleSystem.addColorRemapGradient(0.3, 0.2, 0.85);
particleSystem.addColorRemapGradient(0.35, 0.4, 0.85);
particleSystem.addColorRemapGradient(0.4, 0.5, 0.9);
particleSystem.addColorRemapGradient(0.5, 0.95, 1.0);
particleSystem.addColorRemapGradient(1.0, 0.95, 1.0);

The color remap gradients define a min and max that will vary over the particle lifetime. The index is then remapped from [min, max] to [0, 1] with this formula: finalIndex = clamp((index - min) / (max - min), 0.0, 1.0).

With remap over lifetime of particle: Ramp Gradient With Remap Over Liftetime

Ultimately you can also remap the alpha value generated per pixel with:

particleSystem.addAlphaRemapGradient(0, 0, 0.1);
particleSystem.addAlphaRemapGradient(1.0, 0.1, 0.8);

The alpha remap will compute the final index value using this formula: finalIndex = clamp((textureAlpha * particleColorAlpha * rampColor.a - min) / (max - min), 0.0, 1.0).

Particle blending

There are different ways that particles are blended with the scene and these are set with blendMode.

particleSystem.blendMode = BABYLON.ParticleSystem.BLENDMODE_ONEONE;
particleSystem.blendMode = BABYLON.ParticleSystem.BLENDMODE_STANDARD;
  • BLENDMODE_ONEONE - colors are added without alpha affecting the result, default;
  • BLENDMODE_STANDARD - colors are added using particle’s alpha (ie. color (1 - alpha) + particleColor alpha).
  • BLENDMODE_ADD - colors are added but only particle color uses particle’s alpha (ie. color + particleColor * alpha).
  • BLENDMODE_MULTIPLY - colors are multiplied and added to (1 - alpha) (ie. color * particleColor + 1 - alpha).
  • BLENDMODE_MULTIPLYADD - two passes rendering with BLENDMODE_MULTIPLY and then BLENDMODE_ADD.

Billboard Modes

By default all particles are rendered as billboards, that is to face the camera. But you can decide to instead align them with particle direction with 

particleSystem.isBillboardBased = false;

When billboard is enabled you can decide to either have a full billboard (on all axes) or only on Y axis with this code:

particleSystem.billboardMode = BABYLON.ParticleSystem.BILLBOARDMODE_Y;

You can also use stretched billboard which will be like a full billboard mode but with an additional rotation to align particles with their direction.

particleSystem.billboardMode = BABYLON.ParticleSystem.BILLBOARDMODE_STRETCHED;

Examples

Billboard mode Y - steam: Billboard Mode Y Billboard false - spherical: Billboard Mode False Multiply blend mode - smoke pillar: Multiply Blend Mode Add blend mode and billboard mode stretched - sparks (select scene, press space): Add Blend Mode And Stretched Billboard Mode Ramp and blend - explosion (select scene, press space): Ramp and Blend