WebGL之点精灵的旋转(Rotation Sprite)
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var VSHADER_SOURCE =[ "attribute vec4 a_Position;", "uniform mat4 u_ProjMatrix;", "uniform float u_PointSize;", "void main() {", " gl_PointSize = u_PointSize;", " gl_Position = u_ProjMatrix * a_Position;", "}" ].join("\n") var FSHADER_SOURCE = [ ‘precision mediump float;‘, "uniform sampler2D u_Sampler;", "uniform float u_Angle" "void main() {", " float x=gl_PointCoord.x-0.5;", " float y=gl_PointCoord.y-0.5;", " float nx=(cos(u_Angle) * x - sin(u_Angle ) * y);", " float ny = (sin( u_Angle ) * x + cos( u_Angle ) * y);", " gl_FragColor = texture2D( u_Sampler, vec2( nx+0.5,ny+0.5) );", "}" ].join("\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 intialize shaders.‘); return; } var projMatrix4=new Matrix4(); projMatrix4.setOrtho(-1,1,-1,1,0.0,1.0); var u_projMatrix=gl.getUniformLocation(gl.program,‘u_ProjMatrix‘); gl.uniformMatrix4fv(u_projMatrix,false,projMatrix4.elements); var u_Angle=gl.getUniformLocation(gl.program,‘u_Angle‘); gl.uniform1f(u_Angle,3.14*0.25); var position=gl.getAttribLocation(gl.program,‘a_Position‘); gl.vertexAttrib3f(position,0.0,0.0,0.0); gl.clearColor(0, 0, 0, 1); gl.clear(gl.COLOR_BUFFER_BIT); loadImg(gl); } function loadImg(gl){ var image=new Image(); image.onload=function(){ drawPic(gl,image) } image.src="pic.png"; } function drawPic(gl,image){ var width=image.width; var height=image.height; var pointSize=gl.getUniformLocation(gl.program,"u_PointSize"); gl.uniform1f(pointSize,Math.max(width,height)); var texture=gl.createTexture(); //gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL,1); gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D,texture); gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MAG_FILTER,gl.NEAREST); gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MIN_FILTER,gl.NEAREST); gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_S,gl.CLAMP_TO_EDGE); gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_T,gl.CLAMP_TO_EDGE); gl.uniform1i(gl.getUniformLocation(gl.program,"u_Sampler"),0); gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,gl.RGBA,gl.UNSIGNED_BYTE,image); gl.clear(gl.COLOR_BUFFER_BIT); gl.drawArrays(gl.POINTS,0,1); gl.bindTexture(gl.TEXTURE_2D, null); }
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