我正在使用 OpenGL ES 2.0 着色器生成分形。它运作良好,直到我决定黑白不够,我需要一个调色板。我将调色板作为 1D 纹理传递给着色器,但我得到的只是黑屏。
着色器基于this one ,传递的纹理是 2D (nx1),因为 OpenGL ES 2.0 不允许 1D 纹理,因此像素颜色由
gl_FragColor = texture2D(palette, vec2((j == int(iterations) ? 0.0 : float(j)) / iterations, 0.5));
(我不确定这里的 0.5)。
相关纹理加载代码:
Bitmap bitmap = Bitmap.createBitmap(colors, colors.length, 1, Bitmap.Config.ARGB_8888);
int handle = ShaderUtils.loadTexture(bitmap);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, handle);
GLES20.glUniform1i(paletteHandle, handle);
[...]
public static int loadTexture(Bitmap bitmap)
{
final int[] textureHandle = new int[1];
GLES20.glGenTextures(1, textureHandle, 0);
if (textureHandle[0] == 0)
{
throw new RuntimeException("Error generating texture name.");
}
// Bind to the texture in OpenGL
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);
// Set filtering
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER,
GLES20.GL_NEAREST);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER,
GLES20.GL_NEAREST);
// Load the bitmap into the bound texture.
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
// Recycle the bitmap, since its data has been loaded into OpenGL.
bitmap.recycle();
return textureHandle[0];
}
顶点着色器:
attribute vec4 vPosition;
void main() {
gl_Position = vPosition;
}
fragment 着色器:
precision mediump float;
uniform sampler2D palette;
uniform float centerX;
uniform float centerY;
uniform float scale;
uniform float iterations;
uniform vec2 resolution;
#define maxiter 1024
void main() {
vec2 center = vec2(centerX, centerY);
vec2 coord = vec2(gl_FragCoord.x, gl_FragCoord.y) / resolution;
vec2 c = (coord - center) / scale;
int j = 0;
vec2 z = c;
for(int i = 0; i<maxiter; i++) {
if (float(i) >= iterations) break;
j++;
float x = (z.x * z.x - z.y * z.y) + c.x;
float y = (z.y * z.x + z.x * z.y) + c.y;
if((x * x + y * y) > 4.0) break;
z.x = x;
z.y = y;
}
gl_FragColor = texture2D(palette, vec2((j == int(iterations) ? 0.0 : float(j)) / iterations, 0.5));
// vec3 color = vec3(float(j)/float(iterations));
// gl_FragColor = vec4(color, 1.0);
}
问题是这很难调试。在 IDE 内部,我确保位图包含正确的数据,并且 logcat 中没有 opengl 错误。着色器在没有纹理的情况下工作,所以这可能是这里的问题。可能是什么原因?
最佳答案
你必须为纹理采样器统一设置的值不是纹理对象的“名称”,它必须是纹理单元的索引:
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, handle);
// this is wrong
//GLES20.glUniform1i(paletteHandle, handle);
GLES20.glUniform1i(paletteHandle, 0); // 0, because of GLES20.GL_TEXTURE0
参见 OpenGL 4.6 API Compatibility Profile Specification; 7.10 Samplers; page 154 :
Samplers are special uniforms used in the OpenGL Shading Language to identify the texture object used for each texture lookup. The value of a sampler indicates the texture image unit being accessed. Setting a sampler’s value to
i
selects texture image unit numberi
.
关于android - 在 OpenGL ES 2.0 着色器中使用纹理作为调色板,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49585086/