我正在学习使用AndEngine的opengl着色器，我的目标是使DynamicSpriteBatch具有一些灯光，光线位置将通过vbo传递到spritebatch中的每个绘制调用，这样我就可以在每个sprite上操作光源。
所以我创建了LightSpriteBatch（使用drawtype.dynamic）
public class LightSpriteBatch extends Shape {
// ===========================================================
// Constants
// ===========================================================
private static final float[] VERTICES_TMP = new float[8];
private static final Transformation TRANSFORATION_TMP = new Transformation();
public static final int VERTEX_INDEX_X = 0;
public static final int VERTEX_INDEX_Y = 1;
public static final int COLOR_INDEX = 2;
public static final int TEXTURECOORDINATES_INDEX_U = 3;
public static final int TEXTURECOORDINATES_INDEX_V = 4;
public static final int LIGHT_POSITION_INDEX_X = 5;
public static final int LIGHT_POSITION_INDEX_Y = 6
;
public static final int VERTEX_SIZE = 2 + 1 + 2 + 2 ;
public static final int VERTICES_PER_SPRITE = 6;
public static final int SPRITE_SIZE = VERTEX_SIZE * VERTICES_PER_SPRITE;
public static final VertexBufferObjectAttributes VERTEXBUFFEROBJECTATTRIBUTES_DEFAULT = new VertexBufferObjectAttributesBuilder(4)
.add(ShaderProgramConstants.ATTRIBUTE_POSITION_LOCATION, ShaderProgramConstants.ATTRIBUTE_POSITION, 2, GLES20.GL_FLOAT, false)
.add(ShaderProgramConstants.ATTRIBUTE_COLOR_LOCATION, ShaderProgramConstants.ATTRIBUTE_COLOR, 4, GLES20.GL_UNSIGNED_BYTE, true)
.add(ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES_LOCATION, ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES, 2, GLES20.GL_FLOAT, false)
.add(LightShader.ATTRIBUTE_LIGHT_POSITION_LOCATION, LightShader.ATTRIBUTE_LIGHT_POSITION, 2, GLES20.GL_FLOAT, false)
.build();
LightShader
public class LightShader extends ShaderProgram {
// ===========================================================
// Constants
// ===========================================================
private static LightShader INSTANCE;
public static final String ATTRIBUTE_LIGHT_POSITION = "a_lightPosition";
public final static int ATTRIBUTE_LIGHT_POSITION_LOCATION = 4;
public static final String VERTEXSHADER =
"uniform mat4 " + ShaderProgramConstants.UNIFORM_MODELVIEWPROJECTIONMATRIX + ";\n" +
"attribute vec4 " + ShaderProgramConstants.ATTRIBUTE_POSITION + ";\n" +
"attribute vec4 " + ShaderProgramConstants.ATTRIBUTE_COLOR + ";\n" +
"attribute vec2 " + ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES + ";\n" +
"attribute vec2 " + LightShader.ATTRIBUTE_LIGHT_POSITION + ";\n" +
"varying vec4 " + ShaderProgramConstants.VARYING_COLOR + ";\n" +
"varying vec2 " + ShaderProgramConstants.VARYING_TEXTURECOORDINATES + ";\n" +
"varying vec2 v_lightPosition;\n" +
"void main() {\n" +
" v_lightPosition = "+ LightShader.ATTRIBUTE_LIGHT_POSITION +" ;\n" +
" " + ShaderProgramConstants.VARYING_COLOR + " = " + ShaderProgramConstants.ATTRIBUTE_COLOR + ";\n" +
" " + ShaderProgramConstants.VARYING_TEXTURECOORDINATES + " = " + ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES + ";\n" +
" gl_Position = " + ShaderProgramConstants.UNIFORM_MODELVIEWPROJECTIONMATRIX + " * " + ShaderProgramConstants.ATTRIBUTE_POSITION + ";\n" +
"}";
public static final String FRAGMENTSHADER =
"precision lowp float;\n" +
"uniform sampler2D " + ShaderProgramConstants.UNIFORM_TEXTURE_0 + ";\n" +
"varying lowp vec4 " + ShaderProgramConstants.VARYING_COLOR + ";\n" +
"varying mediump vec2 " + ShaderProgramConstants.VARYING_TEXTURECOORDINATES + ";\n" +
"varying lowp vec2 v_lightPosition;\n" +
"void main() {\n" +
" vec4 tx = texture2D(" + ShaderProgramConstants.UNIFORM_TEXTURE_0 + ", " + ShaderProgramConstants.VARYING_TEXTURECOORDINATES + ") ;"+
" float u_radius = 100.0;"+
" vec2 u_lightPosition = vec2(200-50+v_lightPosition.x,200-50+v_lightPosition.y);"+
" float distance = length( u_lightPosition - gl_FragCoord.xy );"+
" float intensity =( 1.5-min( distance, u_radius )/u_radius)*1.5;"+
" gl_FragColor = vec4(tx.r*intensity,tx.g*intensity,tx.b*intensity,tx.w);"+
"}";
// ===========================================================
// Fields
// ===========================================================
public static int sUniformModelViewPositionMatrixLocation = ShaderProgramConstants.LOCATION_INVALID;
public static int sUniformTexture0Location = ShaderProgramConstants.LOCATION_INVALID;
// ===========================================================
// Constructors
// ===========================================================
private LightShader() {
super(LightShader.VERTEXSHADER, LightShader.FRAGMENTSHADER);
}
public static LightShader getInstance() {
if(LightShader.INSTANCE == null) {
LightShader.INSTANCE = new LightShader();
}
return LightShader.INSTANCE;
}
// ===========================================================
// Getter & Setter
// ===========================================================
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
@Override
protected void link(final GLState pGLState) throws ShaderProgramLinkException {
GLES20.glBindAttribLocation(this.mProgramID, ShaderProgramConstants.ATTRIBUTE_POSITION_LOCATION, ShaderProgramConstants.ATTRIBUTE_POSITION);
GLES20.glBindAttribLocation(this.mProgramID, ShaderProgramConstants.ATTRIBUTE_COLOR_LOCATION, ShaderProgramConstants.ATTRIBUTE_COLOR);
GLES20.glBindAttribLocation(this.mProgramID, ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES_LOCATION, ShaderProgramConstants.ATTRIBUTE_TEXTURECOORDINATES);
GLES20.glBindAttribLocation(this.mProgramID, ShaderProgramConstants.ATTRIBUTE_POSITION_0_LOCATION, ShaderProgramConstants.ATTRIBUTE_POSITION_0);
super.link(pGLState);
LightShader.sUniformModelViewPositionMatrixLocation = this.getUniformLocation(ShaderProgramConstants.UNIFORM_MODELVIEWPROJECTIONMATRIX);
LightShader.sUniformTexture0Location = this.getUniformLocation(ShaderProgramConstants.UNIFORM_TEXTURE_0);
}
@Override
public void bind(final GLState pGLState, final VertexBufferObjectAttributes pVertexBufferObjectAttributes) {
GLES20.glEnableVertexAttribArray(ShaderProgramConstants.ATTRIBUTE_POSITION_0_LOCATION);
super.bind(pGLState, pVertexBufferObjectAttributes);
GLES20.glUniformMatrix4fv(LightShader.sUniformModelViewPositionMatrixLocation, 1, false, pGLState.getModelViewProjectionGLMatrix(), 0);
GLES20.glUniform1i(LightShader.sUniformTexture0Location, 0);
}
@Override
public void unbind(GLState pGLState) throws ShaderProgramException {
GLES20.glDisableVertexAttribArray(ShaderProgramConstants.ATTRIBUTE_POSITION_0_LOCATION);
super.unbind(pGLState);
}
// ===========================================================
// Methods
// ===========================================================
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
}
我还创建了自定义HighPerformanceLightSpriteBatchVBO，我将光位置传递到缓冲区
@Override
public void addWithPackedColor(final ITextureRegion pTextureRegion, final float pX1, final float pY1, final float pX2, final float pY2, final float pColorABGRPackedInt,final float pLightXX,final float pLightYY) {
final float[] bufferData = this.getBufferData();
final int bufferDataOffset = this.mBufferDataOffset;
final float x1 = pX1;
final float y1 = pY1;
final float x2 = pX2;
final float y2 = pY2;
final float u = pTextureRegion.getU();
final float v = pTextureRegion.getV();
final float u2 = pTextureRegion.getU2();
final float v2 = pTextureRegion.getV2();
final float pLightX = pLightXX;
final float pLightY = pLightYY;
if(pTextureRegion.isRotated()) {
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.VERTEX_INDEX_X] = x1;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.VERTEX_INDEX_Y] = y1;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.COLOR_INDEX] = pColorABGRPackedInt;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.TEXTURECOORDINATES_INDEX_U] = u;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.TEXTURECOORDINATES_INDEX_V] = v;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.LIGHT_POSITION_INDEX_X] = pLightX;
bufferData[bufferDataOffset + 0 * LightSpriteBatch.VERTEX_SIZE + LightSpriteBatch.LIGHT_POSITION_INDEX_Y] = pLightY;
所有这一切都有效但我在片段着色器中读取这个光照位置时遇到了问题。如果渲染纹理，我需要做些什么计算来正确计算光位置和位置之间的距离？
DynamicLightSpriteBatch sb = new DynamicLightSpriteBatch(mTextureSprite,10,getVertexBufferObjectManager()) {
@Override
protected boolean onUpdateSpriteBatch() {
draw(mTextureSpriteRegion, 0f, 0f, 400f, 400f, 0f, 1.0f, 1.0f, 1.0f, 1.0f,100f,100f); // ( 100,100 = lightX & Y )
return true;
}
};
光总是在中心（200-半径/ 2,200-半径/ 2），它应该移动100,100作为最后的参数
答案 0 :(得分：0)
如果我理解正确你想要的是片段着色器中的相对光位置，它对于每个像素是不同的。为此，您需要访问顶点着色器中的模型视图和投影矩阵，并计算要将精灵传递给片段着色器的up和right向量。然后在片段着色器中将此（乘以texcoord）添加到精灵中心位置，以获得每个阴影片段（精灵的每个像素）的世界空间位置。从光线位置减去它，瞧！
请注意，在着色器代码中，顶点/片段着色器中的varying变量似乎有不同的精度说明符。这可能会导致问题（变化可能不会链接，因此顶点着色器中输出的值将被丢弃，并且片段着色器中的输入值未定义）。这是OpenGL的一个黑暗角落，有些原因是需要能够任意混合和匹配不同的顶点和片段着色器。