Glsl.kt

vertex shader:

#version 300 es

#ifdef GL_ES
precision mediump float;
#endif

in vec4 Vertex;
uniform mat4 viewProjMatrix;

void main(void) {
    gl_Position = viewProjMatrix * Vertex;
}

matrix:
    internal var viewProjMatrix = Matrix4()
        .makeOrthographic(-0.5, 0.5, -.5, .5, 1.0, 10.0)
        .lookAt(
            Vector3(0.0f, 0.0f, 1.0f),
            Vector3(0.0f, 0.0f, 0.0f),
            Vector3(0.0f, 1.0f, 0.0f)
        )


quad:

    inner class Quad {
        private val vertices = arrayOf(
            // Left bottom triangle
            -0.5f, 0.5f, 0f,
            -0.5f, -0.5f, 0f,
            0.5f, -0.5f, 0f,
            // Right top triangle
            0.5f, -0.5f, 0f,
            0.5f, 0.5f, 0f,
            -0.5f, 0.5f, 0f
        )
        private val indices = arrayOf(0, 1, 2, 3, 4, 5).map { it.toShort() }.toTypedArray()

        private var quadVertexBuffer: WebGLBuffer? = null
        private var indexBuffer: WebGLBuffer? = null

        init {
            quadVertexBuffer = gl.createBuffer()
            gl { gl.bindBuffer(GL.ARRAY_BUFFER, quadVertexBuffer) }
            gl { gl.bufferData(GL.ARRAY_BUFFER, Float32Array(vertices), GL.STATIC_DRAW); }

            indexBuffer = gl.createBuffer()
            gl { gl.bindBuffer(GL.ELEMENT_ARRAY_BUFFER, indexBuffer); }
            gl { gl.bufferData(GL.ELEMENT_ARRAY_BUFFER, Uint16Array(indices), GL.STATIC_DRAW); }

            val vertexAttr = gl { gl.getAttribLocation(program, "Vertex") }
            gl { gl.vertexAttribPointer(vertexAttr, 3, GL.FLOAT, false, 0, 0) }
            gl { gl.enableVertexAttribArray(vertexAttr) }

            gl { gl.bindBuffer(GL.ARRAY_BUFFER, null) }
            gl { gl.bindBuffer(GL.ELEMENT_ARRAY_BUFFER, null); }
        }

        internal fun render() {
            gl { gl.bindBuffer(GL.ARRAY_BUFFER, quadVertexBuffer) }
            gl { gl.bindBuffer(GL.ELEMENT_ARRAY_BUFFER, indexBuffer); }

            // Draw the vertices
            gl { gl.drawElements(GL.TRIANGLES, indices.size, GL.UNSIGNED_SHORT,0) }

            gl { gl.bindBuffer(GL.ARRAY_BUFFER, null) }
            gl { gl.bindBuffer(GL.ELEMENT_ARRAY_BUFFER, null); }
        }

        private fun release() {
            gl { gl.bindBuffer(GL.ARRAY_BUFFER, null) }
            gl { gl.deleteBuffer(quadVertexBuffer) }
            gl { gl.deleteBuffer(indexBuffer) }
        }
    }