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function drawScene(gl, programInfo, buffers) {
gl.clearColor(0.0, 0.0, 0.0, 1.0); // Clear to black, fully opaque
gl.clearDepth(1.0); // Clear everything
gl.enable(gl.DEPTH_TEST); // Enable depth testing
gl.depthFunc(gl.LEQUAL); // Near things obscure far things
// Clear the canvas before we start drawing on it.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Create a perspective matrix, a special matrix that is
// used to simulate the distortion of perspective in a camera.
// Our field of view is 45 degrees, with a width/height
// ratio that matches the display size of the canvas
// and we only want to see objects between 0.1 units
// and 100 units away from the camera.
const fieldOfView = (45 * Math.PI) / 180; // in radians
const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
const zNear = 0.1;
const zFar = 100.0;
const projectionMatrix = mat4.create();
// note: glmatrix.js always has the first argument
// as the destination to receive the result.
mat4.perspective(projectionMatrix, fieldOfView, aspect, zNear, zFar);
// Set the drawing position to the "identity" point, which is
// the center of the scene.
const modelViewMatrix = mat4.create();
// Now move the drawing position a bit to where we want to
// start drawing the square.
mat4.translate(
modelViewMatrix, // destination matrix
modelViewMatrix, // matrix to translate
[-0.0, 0.0, -6.0],
); // amount to translate
// Tell WebGL how to pull out the positions from the position
// buffer into the vertexPosition attribute.
setPositionAttribute(gl, buffers, programInfo);
// Tell WebGL to use our program when drawing
gl.useProgram(programInfo.program);
// Set the shader uniforms
gl.uniformMatrix4fv(
programInfo.uniformLocations.projectionMatrix,
false,
projectionMatrix,
);
gl.uniformMatrix4fv(
programInfo.uniformLocations.modelViewMatrix,
false,
modelViewMatrix,
);
{
const offset = 0;
const vertexCount = 4;
gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
}
}
// Tell WebGL how to pull out the positions from the position
// buffer into the vertexPosition attribute.
function setPositionAttribute(gl, buffers, programInfo) {
const numComponents = 2; // pull out 2 values per iteration
const type = gl.FLOAT; // the data in the buffer is 32bit floats
const normalize = false; // don't normalize
const stride = 0; // how many bytes to get from one set of values to the next
// 0 = use type and numComponents above
const offset = 0; // how many bytes inside the buffer to start from
gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
gl.vertexAttribPointer(
programInfo.attribLocations.vertexPosition,
numComponents,
type,
normalize,
stride,
offset,
);
gl.enableVertexAttribArray(programInfo.attribLocations.vertexPosition);
}
export { drawScene };