在Java中将4浮点颜色变为一种浮点，然后在openGL ES 2.0着色器中再次返回 [英] 4 float color to one float in java, and back again in openGL ES 2.0 shader

问题描述

我正在尝试向着色器发送的每个顶点都发送一种颜色，但是仅使用一个浮点值.我觉得很奇怪，您不能在每个顶点上发送4个字节作为属性，但是感觉我不可能尝试将RGBA打包到单个float变量中，所以这是我的代码:

I am trying to send one color with every vertex that goes in to the shader, but in only one float value. I think is weird that you cannot send 4 bytes as attributes with every vertex, but sense it's not possible I am going to try to pack RGBA in a single float variable, so this is my code:

Jave代码(将值打包为一个浮点数):

Jave code (that packs the values in one float):

private float fourfColor2One(float r, float g, float b, float a)
{
    long temp = (byte) (r * 255);
    float res = temp << 24;

    temp = (byte) (g * 255);
    res += temp << 16;

    temp = (byte) (b * 255);
    res += temp << 8;

    temp = (byte) (a * 255);
    res += temp;

    return res;
}

着色器代码(将其打包): 顶点着色器:

Shadercode (that packs it up): Vertex shader:

attribute vec4 vPosition;
attribute float fColor;
uniform vec2 vCamPos;
uniform float fZoom;
uniform mat4 m_projectionMat;
varying float v_Color;
void main() {
  vec4 position = vec4(vPosition.x - vCamPos.x - 16., vPosition.y - vCamPos.y - ((32. / "+ GraphicsRenderer.mScnR +") / 2.), -1., 1.);
  position = position * m_projectionMat;
  gl_Position = vec4(position.xy * fZoom, -1, 1);
  v_Color = fColor;
}

片段着色器:

precision mediump float;
varying float v_Color;
void main() {
   uint temp = uint(v_Color);
   float r = temp & 0xf000;
   float g = temp & 0x0f00;
   float b = temp & 0x00f0;
   float a = temp & 0x000f;
    gl_FragColor = vec4(r, g, b, a);
}

所以我有三个问题:

1. 这个概念甚至可能吗?

1. Is this concept even possible?

转换不正确，对吧?我假设当我从float转换为float时，转换不会保留位的顺序，而是保留它在该数据类型中表示的值，对吧?

The conversions is not correct, right? I assume that when I convert from and to float, the conversion does not retain the order of the bit, but rather the values it represent in that datatype, right?

现在，当我运行时，着色器使我返回-1: glGetAttribLocation(mShaderHandle，"fColor"); 但是，这一行只适用于以下一行: glGetAttribLocation(mShaderHandle，"vPosition");

Right now the shader gives me -1 back when i run: glGetAttribLocation(mShaderHandle, "fColor"); But this one works one line before: glGetAttribLocation(mShaderHandle, "vPosition");

那么，有什么想法吗?

提前谢谢！

推荐答案

我会转换

private static int fourfColor2One(float r, float g, float b, float a) {
    return (Math.round(r * 255) << 24) + 
           (Math.round(g * 255) << 16) +
           (Math.round(b * 255) << 8) +
           Math.round(a * 255);
}

这假设您的着色器"的缩放比例为0.0到1.0，而您假设缩放比例为0.0到255.0

This assumes your scale is 0.0 to 1.0 in your "shader" you assume the scale is 0.0 to 255.0

一些伪代码"可以逆转这种情况

Some "pseudo code" to reverse this

float r = (temp & 0xf000)/255.0;
float g = (temp & 0x0f00)/255.0;
float b = (temp & 0x00f0)/255.0;
float a = (temp & 0x000f)/255.0;

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