通过VBO向片段着色器传递额外数据 - DynamicSpriteBatch

Question

通过VBO向片段着色器传递额外数据 - DynamicSpriteBatch

8

我正在学习使用AndEngine编写OpenGL着色器，我的目标是使用一些光线着色器来创建DynamicSpriteBatch，其中光源位置将通过vbo传递给每个spritebatch的绘制调用，以便我可以在每个sprite上操纵光源。

因此，我已创建了LightSpriteBatch（具有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();

轻量级着色器

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
// ===========================================================

我还创建了自定义的HighPerformanceLightSpriteBatchVBO，将光源位置传递到缓冲区中。

@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;

虽然当前的代码可以工作，但是我在片元着色器中读取光源位置时遇到了问题。请问我需要进行怎样的计算才能准确地计算出渲染纹理时光源位置和当前位置之间的距离？

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;
        }
    };

光源始终位于中心位置 (200-半径/2, 200-半径/2)，并应该通过最后的参数向右移动100个单位，向下移动100个单位。

- Paweł

1

你能同时发布着色器代码吗？ - Kimi

有（从顶部开始的第二个片段）LightShader。 - Paweł

1个回答

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可以查看英文原文，
原文链接

- the swine · Answer 1

如果我理解正确，您想在片段着色器中获得相对光位置，每个像素的位置都不同。为此，您需要在顶点着色器中访问模型视图和投影矩阵，并计算传递给片段着色器的精灵的up和right向量。然后，在片段着色器中将其（乘以纹理坐标）添加到精灵中心位置，以获取每个着色片段（精灵的每个像素）的世界空间位置。从光源位置中减去这个位置，就可以得到相对光位置！

请注意，在您的着色器代码中，顶点/片段着色器中的varying变量具有不同的精度说明符。这可能会导致问题（varyings可能无法链接，因此在顶点着色器中输出的值被丢弃，在片段着色器中输入的值未定义）。这是OpenGL的一个黑暗角落，部分原因是要求能够任意混合和匹配不同的顶点和片段着色器。