GLES20.glUniform4fv和fragshader

问题描述

好的，所以我试图在一个对象中循环并使用多种颜色，但似乎无法弄清楚并诚实地将头发撕开，但是此代码来自Android指南，我一直在玩现在绕过它一分钟，并尝试了许多不同的方法，但总是最后回到问题所在：“是片段着色器，还是我只是在使用函数GLES20.glUniform4fv（colorHandle，2，color，0）错误？如果不能接受颜色的数组参数，为什么要有一个'count'值和一个数组参数？”

class Triangle {
    private var mProgram: Int
    private var vPMatrixHandle: Int = 0
    private var positionHandle: Int = 0
    private var mColorHandle: Int = 0
    private val fragmentShaderCode: String =
        "precision mediump float;\n" +
        "uniform vec4 vColor[];\n" +
        "void main() {\n" +
            "\tgl_FragColor = vColor;\n" +
        "}"
    private val vertexShaderCode: String =
        "uniform mat4 uMVPMatrix;\n" +
        "attribute vec4 vPosition;\n" +
        "void main() {\n" +
            "\tgl_Position = uMVPMatrix * vPosition;\n" +
        "}"

    private val COORDS_PER_VERTEX: Int = 3
    private var triangleCoords: FloatArray = floatArrayOf(
        -0.5f,-0.5f,0.5f,0.5f
    )
    private val color: FloatArray = floatArrayOf(
        0.63671875f,0.76953125f,0.22265625f,1.0f,0.63671875f,0.22953125f,0.78265625f,1.0f
    )
    private val indiceCoords: ByteArray = byteArrayOf(
        0,4,5,1,6,2,7,3,2
    )

    private val vertexCount: Int = triangleCoords.size / COORDS_PER_VERTEX
    private val vertexStride: Int = COORDS_PER_VERTEX * 4

    private var vertexBuffer: FloatBuffer =
        ByteBuffer.allocateDirect(triangleCoords.size * 4).run {
            order(ByteOrder.nativeOrder())
            asFloatBuffer().apply {
                put(triangleCoords)
                position(0)
            }
        }

    private var indiceBuffer: ByteBuffer =
        ByteBuffer.allocateDirect(indiceCoords.size * 4).run {
            order(ByteOrder.nativeOrder()).apply {
                put(indiceCoords)
                position(0)
            }
        }

    init {
        val vertexShader: Int = loadShader(GLES20.GL_VERTEX_SHADER,vertexShaderCode)
        val fragmentShader: Int = loadShader(GLES20.GL_FRAGMENT_SHADER,fragmentShaderCode)
        mProgram = GLES20.glCreateProgram().also {
            GLES20.glAttachShader(it,vertexShader)
            GLES20.glAttachShader(it,fragmentShader)
            GLES20.glLinkProgram(it)
        }
    }

    fun loadShader(type: Int,shaderCode: String): Int {
        return GLES20.glCreateShader(type).also { shader ->
            GLES20.glShaderSource(shader,shaderCode)
            GLES20.glCompileShader(shader)
        }
    }

    fun draw(mvpMatrix: FloatArray) {
        GLES20.glUseProgram(mProgram)
        positionHandle = GLES20.glGetAttribLocation(mProgram,"vPosition").also {
            GLES20.glEnableVertexAttribArray(it)
            GLES20.glVertexAttribPointer(
                it,COORDS_PER_VERTEX,GLES20.GL_FLOAT,false,vertexStride,vertexBuffer
            )
            mColorHandle = GLES20.glGetUniformLocation(mProgram,"vColor").also { colorHandle ->
                GLES20.glUniform4fv(colorHandle,color,0)
            }
            vPMatrixHandle = GLES20.glGetUniformLocation(mProgram,"uMVPMatrix")
            GLES20.glUniformMatrix4fv(vPMatrixHandle,mvpMatrix,0)
            GLES20.glDrawElements(GL10.GL_TRIANGLES,36,GL10.GL_UNSIGNED_BYTE,indiceBuffer)
            GLES20.glDisableVertexAttribArray(it)
        }
    }
}

解决方法

如果要将颜色与顶点关联，则必须添加其他属性。颜色的数量必须与顶点的数量相同。

将颜色属性添加到顶点着色器（attribute vec4 vColor;）。将属性从顶点着色器传递到片段着色器（varying vec4 color;）：

private val fragmentShaderCode: String =
    "precision mediump float;\n" +
    "varying vec4 color;\n" +
    "void main() {\n" +
        "\tgl_FragColor = color;\n" +
    "}"
private val vertexShaderCode: String =
    "uniform mat4 uMVPMatrix;\n" +
    "attribute vec4 vPosition;\n" +
    "attribute vec4 vColor;\n" +
    "varying vec4 color;\n" +
    "void main() {\n" +
        "\tcolor = vColor;\n" +
        "\tgl_Position = uMVPMatrix * vPosition;\n" +
    "}"

定义8种颜色的数组。例如：

private val COORDS_PER_COLOR: Int = 4
private val color: FloatArray = floatArrayOf(
    0.63671875f,0.76953125f,0.22265625f,1.0f,0.63671875f,0.22953125f,0.78265625f,0.0f,1.0f
)

private val colorCount: Int = color.size / COORDS_PER_COLOR
private val colorStride: Int = COORDS_PER_COLOR * 4

为颜色属性创建缓冲区：

private var colorBuffer: FloatBuffer =
    ByteBuffer.allocateDirect(color.size * 4).run {
        order(ByteOrder.nativeOrder())
        asFloatBuffer().apply {
            put(color)
            position(0)
        }
    }

指定颜色属性数组：

mColorHandle = GLES20.glGetAttribLocation(mProgram,"vColor").also { colorHandle ->
    GLES20.glEnableVertexAttribArray(colorHandle)
    GLES20.glVertexAttribPointer(
        colorHandle,COORDS_PER_COLOR,GLES20.GL_FLOAT,false,colorStride,colorBuffer
    )
}

,

如果要使用“统一”数组（vColor []），请在声明中显式指定数组大小。

private val fragmentShaderCode: String =
        "precision mediump float;\n" +
                "uniform vec4 vColor[2];\n" +
                "varying vec4 vParam;" +
                "void main() {\n" +
                "\tgl_FragColor = vColor[int(step(vParam.x * vParam.y * vParam.z,0.0))];\n" +
                "}"
private val vertexShaderCode: String =
        "uniform mat4 uMVPMatrix;\n" +
                "attribute vec4 vPosition;\n" +
                "varying vec4 vParam;" +
                "void main() {\n" +
                "\tgl_Position = uMVPMatrix * vPosition;\n" +
                "\tvParam = vPosition;" +
                "}"