Modeling/Transformation Examples Modeling a colored cube Hierarchical modeling

Modeling a Colored Cube cube & cubev of Chapter 4

Cube function colorCube() { quad( 1, 0, 3, 2 ); quad( 2, 3, 7, 6 ); quad( 3, 0, 4, 7 ); quad( 6, 5, 1, 2 ); quad( 4, 5, 6, 7 ); quad( 5, 4, 0, 1 ); } (-0.5,-0.5,0.5) (0.5,0.5,-0.5)

Inward and Outward-Pointing Faces

Divide a Quadrilateral into Two Triangles aa bc d c d b

Color Interpolation by Rasterizaton Interpolation using barycentric coordinates

Transformation Performed at Vertex Shader attribute vec4 vPosition; attribute vec4 vColor; varying vec4 fColor; uniform vec3 theta; void main() { // Remeber: thse matrices are column-major mat4 rx = mat4( ……); mat4 ry = mat4( ….. ); mat4 rz = mat4( …… ); fColor = vColor; gl_Position = rz * ry * rx * vPosition; }

Draw with gl.drawArrays var axis = 0; var theta = [ 0, 0, 0 ]; var thetaLoc; thetaLoc = gl.getUniformLocation(program, "theta"); theta[axis] += 2.0; gl.uniform3fv(thetaLoc, theta); gl.drawArrays( gl.TRIANGLES, 0, NumVertices );

Draw with gl.drawElements (Array of Indices) var indices = [ 1, 0, 3, 3, 2, 1, 2, 3, 7, 7, 6, 2, 3, 0, 4, 4, 7, 3, 6, 5, 1, 1, 2, 6, 4, 5, 6, 6, 7, 4, 5, 4, 0, 0, 1, 5 ]; (-0.5,-0.5,0.5) (0.5,0.5,-0.5)

Draw with gl.drawElements (Create Buffers) // array element buffer var iBuffer = gl.createBuffer(); gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, iBuffer); gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint8Array(indices), gl.STATIC_DRAW); // color array atrribute buffer var cBuffer = gl.createBuffer(); gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer ); gl.bufferData( gl.ARRAY_BUFFER, flatten(vertexColors), gl.STATIC_DRAW ); // vertex array attribute buffer var vBuffer = gl.createBuffer(); gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer ); gl.bufferData( gl.ARRAY_BUFFER, flatten(vertices), gl.STATIC_DRAW );

Draw with gl.drawElements var axis = 0; var theta = [ 0, 0, 0 ]; var thetaLoc; thetaLoc = gl.getUniformLocation(program, "theta"); theta[axis] += 2.0; gl.uniform3fv(thetaLoc, theta); gl.drawElements( gl.TRIANGLES, numVertices, gl.UNSIGNED_BYTE, 0 );

Hierarchical Modeling RobotArm & figure of Chapter 9

Robot Arm

Each Individual Part function lowerArm() { var s = scale4(LOWER_ARM_WIDTH, LOWER_ARM_HEIGHT, LOWER_ARM_WIDTH); var instanceMatrix = mult( translate( 0.0, 0.5 * LOWER_ARM_HEIGHT, 0.0 ), s); var t = mult(modelViewMatrix, instanceMatrix); gl.uniformMatrix4fv( modelViewMatrixLoc, false, flatten(t) ); gl.drawArrays( gl.TRIANGLES, 0, NumVertices ); }

The render() Function modelViewMatrix = rotate(theta[Base], 0, 1, 0 ); base(); modelViewMatrix = mult(modelViewMatrix, translate(0.0, BASE_HEIGHT, 0.0)); modelViewMatrix = mult(modelViewMatrix, rotate(theta[LowerArm], 0, 0, 1 )); lowerArm(); modelViewMatrix = mult(modelViewMatrix, translate(0.0, LOWER_ARM_HEIGHT, 0.0)); modelViewMatrix = mult(modelViewMatrix, rotate(theta[UpperArm], 0, 0, 1) ); upperArm();

Vertex Shader attribute vec4 vPosition; attribute vec4 vColor; varying vec4 fColor; uniform mat4 modelViewMatrix; uniform mat4 projectionMatrix; void main() { fColor = vColor; gl_Position = projectionMatrix * modelViewMatrix * vPosition; }

Figure

Binary Tree Representation of a Regular Tree function createNode(transform, render, sibling, child){ var node = { transform: transform, render: render, sibling: sibling, child: child, } return node; }

Each Individual Part function rightLowerArm() { instanceMatrix = mult(modelViewMatrix, translate(0.0, 0.5 * lowerArmHeight, 0.0) ); instanceMatrix = mult(instanceMatrix, scale4(lowerArmWidth, lowerArmHeight, lowerArmWidth) ); gl.uniformMatrix4fv(modelViewMatrixLoc, false, flatten(instanceMatrix)); for(var i =0; i<6; i++) gl.drawArrays(gl.TRIANGLE_FAN, 4*i, 4); }

Build the Figure function initNodes(Id) { var m = mat4(); switch(Id) { case leftUpperArmId: m = translate(-(torsoWidth+upperArmWidth), 0.9*torsoHeight, 0.0); m = mult(m, rotate(theta[leftUpperArmId], 1, 0, 0)); figure[leftUpperArmId] = createNode( m, leftUpperArm, rightUpperArmId, leftLowerArmId ); break; }

Matrix Stack var modelViewMatrix; var stack = []; stack.push(modelViewMatrix); modelViewMatrix = stack.pop();

Tree Traversal function traverse(Id) { if(Id == null) return; stack.push(modelViewMatrix); modelViewMatrix = mult(modelViewMatrix, figure[Id].transform); figure[Id].render(); if(figure[Id].child != null) traverse(figure[Id].child); modelViewMatrix = stack.pop(); if(figure[Id].sibling != null) traverse(figure[Id].sibling); }

The render Function var render = function() { gl.clear( gl.COLOR_BUFFER_BIT ); traverse(torsoId); requestAnimFrame(render); }