luma.gl/docs/api-reference/engine/model.md

Model

Proposed luma.gl v9 API. Open for comments.

The Model is the primary class for most luma.gl applications.

A Model brings together a range of different luma.gl functions in one class. It holds all the data necessary to perform draw calls:

• shaders (via a Program instance)
• bindings these can reference uniforms and textures.
• attributes (holds a [Mesh] or a Geometry instance, plus any additional attributes for instanced rendering)

The Model class integrates with the @luma.gl/shadertools shader module system: see Shader Assembly.

TBD

• Automatically creates GPU Buffers from typed array attributes
• Detailed debug logging of draw calls
• Exposes the functionality provided by the managed WebGL resources

Usage

Provide attribute data using Geometry object

Create model object by passing shaders, uniforms, geometry and render it by passing updated uniforms.

// construct the model.
const model =  new Model(device, {
  vs: VERTEX_SHADER,
  fs: FRAGMENT_SHADER,
  uniforms: {uSampler: texture},
  geometry: geometryObject,
})

// and on each frame update any uniforms (typically matrices) and call render.
model
  .setUniforms({
    uPMatrix: currentProjectionMatrix,
    uMVMatrix: current ModelViewMatrix
  })
  .draw();

Provide attribute data using Buffer

When using Buffer objects, data remains on GPU and same Buffer object can be shared between multiple models.

// construct the model.
const model = new Model(device, {
  vs: VERTEX_SHADER,
  fs: FRAGMENT_SHADER,
  topology: 'triangle-list',
  vertexCount: 3,
  attributes: {
    attributeName1: bufferObject,
    attributeName2: device.createBuffer(new Float32Array(...))
  },
  uniforms: {uSampler: texture},
})

// and on each frame update any uniforms (typically matrices) and call render.
model
  .setUniforms({
    uPMatrix: currentProjectionMatrix,
    uMVMatrix: currentModelViewMatrix
  })
  .draw();

Provide attribute data using VertexArray object

A VertexArray object can be build and passed to Model.draw() to provide attribute data. Attribute data can be changed by changing VertexArray object.

// construct the model.
const model = new Model(device, {
  vs: VERTEX_SHADER,
  fs: FRAGMENT_SHADER,
  uniforms: {uSampler: texture},
  drawMode: gl.TRIANGLE_FAN,
  vertexCount: 3
});

const ATTRIBUTE1_LOCATION = 0;
const ATTRIBUTE2_LOCATION = 1;
const vertexArray1 = device.createVertexArray({
  buffers: {
    [ATTRIBUTE1_LOCATION]: buffer1,
    [ATTRIBUTE2_LOCATION]: buffer2
  }
});
const vertexArray2 = device.createVertexArray({
  buffers: {
    [ATTRIBUTE1_LOCATION]: buffer3,
    [ATTRIBUTE2_LOCATION]: buffer4
  }
});

//Render using attribute data from vertexArray1.
model.draw({
  uniforms: {
    uPMatrix: currentProjectionMatrix,
    uMVMatrix: currentModelViewMatrix
  },
  vertexArray: vertexArray1
});

// Switch attribute data to vertexArray2
model.setUniforms({
  uPMatrix: currentProjectionMatrix,
  uMVMatrix: currentModelViewMatrix
})
model.setVertexArray(vertexArray2);
model.draw({...});

Properties

Property	Type	Description
vs	Shader | string	A vertex shader object, or source as a string.
fs	Shader | string	A fragment shader object, or source as a string.
layout	ShaderLayout	Describes how shader attributes and bindings are laid out.
modules		shader modules to be applied (shadertools).
pipeline		pre created program to use, when provided, vs, ps and modules are not used.
topology?		'point-list', 'line-list', 'line-strip', 'triangle-list' or 'triangle-strip',
parameters?	RenderPipelineParameters

• programManager | | ProgramManager to use for program creation and caching. |
• varyings | (WebGL 2) | An array of vertex shader output variables, that needs to be recorded (used in TransformFeedback flow). |
• bufferMode | (WebGL 2) | Mode to be used when recording vertex shader outputs (used in TransformFeedback flow). Default value is gl.SEPARATE_ATTRIBS. |
• transpileToGLSL100 | | Transpile vertex and fragment shaders to GLSL 1.0. |

Properties

moduleSettings: object

any uniforms needed by shader modules.

uniforms: object

uniform values to be used for drawing.

onBeforeRender

function to be called before every time this model is drawn.

onAfterRender

function to be called after every time this model is drawn.

Methods

Model(device: Device, props: ModelProps)

The constructor for the Model class. Use this to create a new Model.

destroy()

Free WebGL resources associated with this model

isAnimated(): boolean

Returns true if the model is animated (i.e. needs to be redrawn every frame).

getProgram(): Program

Get model's Program instance

getUniforms(): object

Returns map of currently stored uniforms

setUniforms(uniforms: object); this

Stores named uniforms {key, value}

updateModuleSettings(moduleSettings: object); this

draw(options: object): boolean

Renders the model with provided uniforms, attributes and samplers

model.draw({
  moduleSettings = null,
  uniforms = {},
  attributes = {},
  samplers = {},
  parameters = {},
  settings,
  framebuffer = null,
  vertexArray = null,
  transformFeedback = null
});

Model.draw() calls Program.draw() but adds and extends the available parameters as follows:

• moduleSettings=null (Object) - any uniforms needed by shader modules.
• attributes={} (Object) - attribute definitions to be used for drawing. In additions to Buffer and constant values, Models can also accept typed arrays and attribute descriptor objects which it converts to buffers.
• uniforms={} (Object) - uniform values to be used for drawing. In addition to normal uniform values, Model can also accept function valued uniforms which will be evaluated before every draw call.
• animationProps (Object) - if any function valued uniforms are set on the Model, animationProps must be provided to the draw call. The animationProps are passed as parameter to the uniform functions.

The remaining draw options are passed directly to Program.draw():

• uniforms={} (Object) - uniform values to be used for drawing.
• samplers={} (Object) - texture mappings to be used for drawing.
• parameters={} (Object) - temporary gl settings to be applied to this draw call.
• framebuffer=null (Framebuffer) - if provided, renders into the supplied framebuffer, otherwise renders to the default framebuffer.
• transformFeedback - an instance TranformFeedback object, that gets activated for this rendering.
• vertexArray - an instance of VertexArray object, that holds required buffer bindings for vertex shader inputs.

transform(options: object); this

Renders the model with provided uniforms, and samplers. Calls Program.draw() with rasterization turned off.

• discard=true (Boolean) - Turns off rasterization
• feedbackBuffers=null (Object) - Optional map of feedback buffers. A TransformFeedback object will be created, initialized with these buffers, and passed to Model.draw.
• unbindModels=[] (Model[]) - Array of models whose VertexAttributes will be temporarily unbound during the transform feeback to avoid triggering a possible Khronos/Chrome bug. .

model.transform({
  discard: false
});