Qt 3D: Simple Custom Material QML Example

This example demonstrates creating a simple custom material.

Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Specifying the Scene

The example uses Scene3D to render a scene which will use the custom material. The scene contains a plane model, which uses the custom material.

Entity {
    id: root

    components: [transform, mesh, material]

    SimpleMaterial {
        id: material
        maincolor: "red"
    }

    Transform {
        id: transform
        rotationX: 45
    }

    PlaneMesh {
        id: mesh
        width: 1.0
        height: 1.0
        meshResolution: Qt.size(2, 2)
    }
}

Specifying the Material

The material is specified in simplecustommaterial/SimpleMaterial.qml using Material type. First the material specifies parameters, which are mapped to the corresponding uniforms in the shaders so that they can be changed from the qml.

property color maincolor: Qt.rgba(0.0, 0.0, 0.0, 1.0)

parameters: [
    Parameter {
        name: "maincolor"
        value: Qt.vector3d(root.maincolor.r, root.maincolor.g, root.maincolor.b)
    }
]

Next we specify which shaders are loaded. Separate versions of the shaders are provided for OpenGL ES 2 and OpenGL renderers.

property string vertex: "qrc:/shaders/gl3/simpleColor.vert"
property string fragment: "qrc:/shaders/gl3/simpleColor.frag"
property string vertexRHI: "qrc:/shaders/gl45/simpleColor.vert"
property string fragmentRHI: "qrc:/shaders/gl45/simpleColor.frag"
property string vertexES: "qrc:/shaders/es2/simpleColor.vert"
property string fragmentES: "qrc:/shaders/es2/simpleColor.frag"

In the vertex shader we simply transform the position by the transformation matrices.

void main()
{
    // Transform position, normal, and tangent to world coords
    worldPosition = vec3(modelMatrix * vec4(vertexPosition, 1.0));

    // Calculate vertex position in clip coordinates
    gl_Position = mvp * vec4(worldPosition, 1.0);
}

In the fragment shader we simply set the fragment color to be the maincolor specified in the material.

uniform vec3 maincolor;
void main()
{
    //output color from material
    fragColor = vec4(maincolor,1.0);
}

Next, we create ShaderPrograms from the shaders.

ShaderProgram {
    id: gl3Shader
    vertexShaderCode: loadSource(parent.vertex)
    fragmentShaderCode: loadSource(parent.fragment)
}
ShaderProgram {
    id: es2Shader
    vertexShaderCode: loadSource(parent.vertexES)
    fragmentShaderCode: loadSource(parent.fragmentES)
}
ShaderProgram {
    id: rhiShader
    vertexShaderCode: loadSource(parent.vertexRHI)
    fragmentShaderCode: loadSource(parent.fragmentRHI)
}

Finally the shader programs are used in the Techniques corresponding to a specific Api profile.

// OpenGL 3.1
Technique {
    filterKeys: [forward]
    graphicsApiFilter {
        api: GraphicsApiFilter.OpenGL
        profile: GraphicsApiFilter.CoreProfile
        majorVersion: 3
        minorVersion: 1
    }
    renderPasses: RenderPass {
        shaderProgram: gl3Shader
    }
},

Example project @ code.qt.io