Continuation of work on visual particles system

[Chaosus]

This is a continuation of my work to the particle system in visual shaders.

Added new shader modes:

• Emit(Custom)
• Process(Custom)

Added nodes:

New Emit nodes:

---

class VisualShaderNodeParticleOutput : VisualShaderNodeOutput

Description: Created automatically in all modes of particle shader.
Have different input ports (depending on the shader mode).

Availability: Everywhere

Common Input ports (on all shader modes):

vec3 velocity - an initial velocity vector, translates to VELOCITY
vec3 color - translates to COLOR.rgb
float alpha - translates to COLOR.a
Transform position - translates to TRANSFORM
float scale
bool active

Emit:

• (Common Input ports)
• float lifetime_scale
• float initial_angle
• float anim_offset

Emit (Custom):

• (Common Input ports)
• vec3 custom
• float custom_alpha

Process:

• (Common Input ports)

Process (Custom):

• (Common Input ports)

End:

• (Common Input ports)

---

class VisualShaderNodeParticleEmitter : VisualShaderNode

Description: Abstract base class for all emitters.

Availability: Emit

Output ports:

• Transform position - position of the particle, need to be connected to the position input port inside VisualShaderNodeParticleOutput.

---

class VisualShaderNodeParticleBoxEmitter : VisualShaderNodeParticleEmitter

Description: Generates a position inside a box.

Availability: Emit

Input ports:

• vec3 extents (default: vec3(1, 1, 1)) - Defines a volume of the box.

Output ports:

• Derived from VisualShaderNodeParticleEmitter

---

class VisualShaderNodeParticleRingEmitter : VisualShaderNodeParticleEmitter

Description: Generates a position inside a ring.

Availability: Emit

Input ports:

• float radius (default:10) - A radius of the ring.
• float inner (default:0) - An inner volume size of the ring.
• float outer (default:0) - An outer volume size of the ring.

Output ports:

• Derived from VisualShaderNodeParticleEmitter

---

class VisualShaderNodeParticleSphereEmitter : VisualShaderNodeParticleEmitter

Description: Generates a position inside a sphere.

Availability: Emit

Input ports:

• float radius (default:10) - A radius of the sphere
• bool use_inner_space (default:true) - if false the particles will generates on a sphere but not inside it.

Output ports:

• Derived from VisualShaderNodeParticleEmitter

---

class VisualShaderNodeParticleTextureEmitter : VisualShaderNodeParticleEmitter

Description: (I think @reduz should implement it himself since I'm not sure how to make it properly).

Availability: Emit

Input ports:

• sampler2D position
• sampler2D normal

Output ports:

• Derived from VisualShaderNodeParticleEmitter

---

class VisualShaderNodeParticleRandomness : VisualShaderNodeParticleEmitter

Description: Generates a random scalar or a vector.

Availability: Everywhere

Properties: Op
Type - OP_TYPE_SCALAR / OP_TYPE_VECTOR which affect a type of result

Input ports:

• float/vec3 min (default: 0.0/vec3(-1, -1, -1)) - a minimum value to generate
• float/vec3 max (default: 1.0/vec3(1, 1, 1)) - a maximum value to generate

Output ports:

• float/vec3 random - a generated value

---

class VisualShaderNodeParticleConeVelocity

Description: Generates a velocity normalized vector inside a cone.

Availability: Emit

Input ports:

• vec3 direction (default: vec3(1, 0, 0)) - a direction vector
• float spread(degrees) (default: 45.0) - spread amount

Output ports:

• vec3 velocity - a velocity normalized vector inside a cone.

---

class VisualShaderNodeParticleAccelerator : VisualShaderNode

Description: Intended to modify particle velocity via time.

Availability: Process

Properties: Mode: MODE_LINEAR/MODE_RADIAL/MODE_TANGENTIAL

Input ports:

• vec3 velocity
• vec3 amount
• float randomness

---

Notes:

• The internal code is mainly copy/pasted from ParticlesMaterial and their outputs is almost identical

• All these new types have a "Particle" suffix to make sorting/seeing of them easy.

[Chaosus]

UPDATE (12/10/2020):

• Added Emit(Custom) and Process(Custom) basic implementation - @reduz is still working on it and there will be separate functions for them in the near future.

• Added Collide mode (and remove End mode for now) - to provide a way to handle colliders
  

• Removed TextureEmitter since I still don't understand how it should work

• Added Emit node to provide a way to emitting - this node does not have outputs instead every instance of it proceeded independently (after Output processing)

- Changed position type of EmitOutput to vector, I think it's better to handle and modify rather than matrix, and logically position associated with vectors. - decided to leave it as it is since the user may want to use whole transform instead (UPDATE 13.10.2020)

• Added rotation_axis port to EmitOutput - now it will work with initial_angle to rotate a mesh transformation
• Removed RotateVector since I think it bloats the engine and perfectly fits to the user extension. (UPDATE 13.10.2020)
• Added PointEmitter (UPDATE 13.10.2020)

[QbieShay]

Can't comment from a code perspective, but I did try out the PR and it already adds pretty good functionalities. It's solid work that will already bring Godot's particle shaders miles ahead in terms of accessibility! 👍

[clayjohn]

I tested this out locally and played around with it for a bit. The only odd thing I noticed was that Velocity was added to VELOCITY in the normal process shader, but overwrote VELOCITY in custom mode. In my opinion, it makes more sense to overwrite velocity every frame in the process shader. That way users can actually control velocity/acceleration. When you specify a value to increase velocity, you are actually specifying acceleration.

[Chaosus]

@clayjohn I removed VELOCITY from custom mode - does it looks ok now?

[Chaosus]

I managed to make scaling and rotation properly work with CurveTexture in Process, but this required an additional matrix to be attached to each particle to keep started transformation: START_TRANSFORM.

The position is being redundant here - since it is inherited from the start function, and being modified by velocity.

[Chaosus]

@reduz said that he would add new built-ins for user data to better performance so I've reverted the changes I made about introducing START_TRANSFORM to the particles renderer. This PR can be merged as it is as it mostly worked properly.

[clayjohn]

I removed VELOCITY from custom mode - does it looks ok now?

I was not suggesting that you remove VELOCITY. I was suggesting that, when you use the Velocity port, you write directly to VELOCITY instead of adding to VELOCITY

[Chaosus]

Sorry, then I wrongly understood you (probably tired). Bring it back and fixed.

[akien-mga]

Thanks!