我正在尝试在WebGL中创建一个程序,该程序允许您通过键盘输入来绘制或创建n尺寸的形状。用户输入侧面的数量以生成具有那么多侧面的形状。因此,如果按“ 3”,将得到一个三角形,如果按“ 4”,将得到一个正方形,如果按“ 5”,将得到一个五边形,等等。
到目前为止,我已经能够创建单独的代码段,这些代码段无需键盘输入即可创建三角形,正方形,五边形等,但是我不确定如何在同一程序中通过n边生成形状。用户/键盘输入。我将如何去做?
到目前为止我的代码示例:
绘制三角形:
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'void main() {\n' +
' gl_Position = a_Position;\n' +
'}\n';
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
function main() {
var canvas = document.getElementById('webgl');
var gl = getWebGLContext(canvas);
if (!gl) {
console.log('Failed to get the rendering context for WebGL');
return;
}
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
console.log('Failed to initialize shaders.');
return;
}
var n = initVertexBuffers(gl);
if (n < 0) {
console.log('Failed to set the positions of the vertices');
return;
}
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, n);
}
function initVertexBuffers(gl) {
var vertices = new Float32Array([
0, 0.5, -0.5, -0.5, 0.5, -0.5
]);
var n = 3; // The number of vertices
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create the buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return -1;
}
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(a_Position);
return n;
}
绘制正方形:
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'void main() {\n' +
' gl_Position = a_Position;\n' +
'}\n';
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
function main() {
var canvas = document.getElementById('webgl');
var gl = getWebGLContext(canvas);
if (!gl) {
console.log('Failed to get the rendering context for WebGL');
return;
}
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
console.log('Failed to initialize shaders.');
return;
}
var n = initVertexBuffers(gl);
if (n < 0) {
console.log('Failed to set the positions of the vertices');
return;
}
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, n);
}
function initVertexBuffers(gl) {
var vertices = new Float32Array([
-1, -1, -1, 1, 1, 1, 1, -1, -1, -1,
]);
var n = 5; // The number of vertices
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create the buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return -1;
}
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(a_Position);
return n;
}
您可以编写一个函数来计算以边数为参数的多边形的顶点位置。
例如,计算给定半径的圆内多边形的极坐标。您可以编写自己的一个。
computePolygonPositions(sides, radius)
{
let positions = []
for (let i=0; i<sides; i++)
{
let i0 = i
let i1 = (i+1) % sides
let theta0 = 2.0 * Math.PI * i0 / sides
let theta1 = 2.0 * Math.PI * i1 / sides
let x0 = radius * Math.cos(theta0)
let y0 = radius * Math.cos(theta0)
let x1 = radius * Math.cos(theta1)
let y1 = radius * Math.cos(theta1)
positions.push(0, 0)
positions.push(x0, y0)
positions.push(x1, y1)
}
return positions
}
当然,您可以升级此功能以添加索引,tex坐标,颜色或所需的任何内容。
一旦完成,只需调用它即可创建一个新的顶点缓冲区,该缓冲区将绑定到ARRAY_BUFFER上,设置布局并启用position属性。