DALi Rendering API Overview

DALi Rendering API Overview

Contents:

1. Rendering API building blocks
   1.1 Renderer
   1.2 PropertyBuffer
   1.3 Geometry
   1.4 Shader
   1.5 Texture
   1.6 Sampler
   1.7 TextureSet
   
2. DALi shader built-ins
   2.1 Shader vertex attributes built-ins
   2.2 Shader uniforms built-ins
   

1. Rendering API building blocks

1. Renderer

The Renderer is responsible for setting graphics API state ( like blending, depth test etc. ) and most of all - issuing a single draw call.

Renderer requires a geometry and shader program to be known upon initialisation. Sample Renderer initialisation may look like below:

using namespace Dali;

Renderer renderer = Renderer::New( geometry, shader );
renderer.SetProperty( Renderer::Property::DEPTH_WRITE_MODE, DepthWriteMode::ON );
renderer.SetProperty( Renderer::Property::DEPTH_FUNCTION, DepthFunction::LESS_EQUAL );
renderer.SetProperty( Renderer::Property::DEPTH_TEST_MODE, DepthTestMode::ON );
renderer.SetTextures( textureSet );

[1] See renderer.h code

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2. PropertyBuffer

PropertyBuffer stores a vertex data. It's an equivalent of the GL buffer object. When used for storing geometry it must be instantiated with known data format defined with use of Property::Map. For example:

Dali::Property::Map vertexFormat;
vertexFormat.Add( "aPosition", Dali::Property::VECTOR3 );
vertexFormat.Add( "aNormal", Dali::Property::VECTOR3 );
vertexFormat.Add( "aTexCoord", Dali::Property::VECTOR2 );
Dali::PropertyBuffer vertexBuffer = Dali::PropertyBuffer::New( vertexFormat );

Example above instantiates a buffer containing data for three vertex shader attributes:

• aPosition - vertex position
• aNormal - vertex normal
• aTexCoord - texture coordinates

[2] See property-buffer.h code

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3. Geometry

Geometry describes vertex input state and topology of the primitives to be drawn. Geometry requires the PropertyBuffer to be known before the initialisation. The Geometry may have attached more than one PropertyBuffer.

geometry = Dali::Geometry::New();
geometry.AddVertexBuffer( vertexBuffer );
geometry.SetType( Geometry::TRIANGLES );

Optionally, the Geometry may specify an index buffer. Then automatically the indexed draw will be enabled.

[3] See geometry.h code

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4. Shader

Shader represents compiled and linked GLSL program. Only Vertex and Fragment shaders are supported. Shader code may be created with use of macro DALI_COMPOSE_SHADER.

For example the vertex and fragment shader source code and Shader instance could be created as shown below:

// vertex shader code
const char* VERTEX_SHADER = DALI_SHADER_COMPOSER(
attribute mediump vec2 aPosition;
attribute mediump vec2 aTexCoord;

uniform mediump mat4 uMvpMatrix;

varying mediump vec2 vTexCoord;

void main()
{
  vTexCoord = aTexCoord;
  gl_Position = uMvpMatrix * vec4( aPosition, 0.0, 1.0 );
}
);

// fragment shader code
const char* FRAGMENT_SHADER = DALI_SHADER_COMPOSER(
precision mediump float;
uniform sampler2D sTexture;

varying mediump vec2 vTexCoord;

void main()
{
  gl_FragColor = texture2D( sTexture, vTexCoord );
}
);

// new shader instance
Dali::Shader shader = Dali::Shader::New( VERTEX_SHADER, FRAGMENT_SHADER );

[4] See shader.h code

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5. Texture

TODO

[5] See texture.h code

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6. Sampler

TODO

[6] See sampler.h code

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7. TextureSet

TextureSet contains one or more texture-sampler pairs. Textures are bind to the shader program in order of appearance on the list. No reflection is used to determine the binding order.

[7] See texture-set.h code

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2. DALi shader built-ins

Shader vertex attributes built-ins

Attribute name	Format	Descritpion
aPosition	Vector2, Vector3	Vertex position
aTexCoord	Vector2	Texture coordinates

Shader uniforms built-ins

Uniform name	Format	Descritpion
uMvpMatrix	Matrix4	ModelViewProjection matrix
uModelView	Matrix4	View matrix
uProjection	Matrix4	Projection matrix
uModelMatrix	Matrix4	Model matrix
uNormalMatrix	Matrix3	Normal matrix
uColor	Vector4	Color RGBA
sTexture	Sampler2D	Main ( default ) texture sampler
sTextureRect	Vec4	Texture rect ( sub-rect )
sEffect	Sampler2D	Secondary ( Effect ) texture sampler
uSize	Vector2, Vector3	Size of geometry

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