错误：0：4："gl_FragColor"：未声明的标识符 &错误：0：4："分配"：无法从"浮点数的均匀 4 分量向量"转换为"浮点数"

Question

OpenGL代码抛出两个错误:

1. ERROR: 0:4: 'gl_FragColor':未声明的标识符
2. ERROR: 0:4: 'assign':无法从'float的均匀四分量向量'转换为'float'

源代码:

mProgram = ShaderHelper.buildProgram(
TextResourceReader.readTextFileFromResource(
context,
R.raw.triangle_fragment_shader
),
TextResourceReader.readTextFileFromResource(
context,
R.raw.triangle_fragment_shader
)
)
// Add program to OpenGL ES environment
GLES20.glUseProgram(mProgram)

ShaderHelper

public static int buildProgram(String vertexShaderSource, String fragmentShaderSource) {
int vertexShader = ShaderHelper.compileVertexShader(vertexShaderSource);
int fragmentShader = ShaderHelper.compileFragmentShader(fragmentShaderSource);
int program = ShaderHelper.linkProgram(vertexShader, fragmentShader);
ShaderHelper.validateProgram(program);
return program;
}
public static int compileVertexShader(String shaderCode) {
return compileShader(GL_VERTEX_SHADER, shaderCode);
}
public static int compileFragmentShader(String shaderCode) {
return compileShader(GL_FRAGMENT_SHADER, shaderCode);
}
private static int compileShader(int type, String shaderCode) {
// Set OpenGL version to 2 in advance, otherwise it will crash here.
final int shaderObjectId = glCreateShader(type);
if (shaderObjectId == 0) {
VLog.w(TAG, "compileShader", "Could not create shader");
return shaderObjectId;
}
glShaderSource(shaderObjectId, shaderCode);
glCompileShader(shaderObjectId);
final int[] compileStatus = new int[1];
glGetShaderiv(shaderObjectId, GL_COMPILE_STATUS, compileStatus, 0);
if (compileStatus[0] == 0) {
glDeleteShader(shaderObjectId);
VLog.d("Compile shader failed" + shaderCode);
return shaderObjectId;
}
//        LogWrapper.d(new String[] {"shaderCode", "GLLogInfo"}, new String[]{shaderCode, glGetShaderInfoLog(shaderObjectId)});;
return shaderObjectId;
}
public static int linkProgram(int vertexShaderId, int fragmentShaderId) {
final int programObjectId = glCreateProgram();
if (programObjectId == 0) {
VLog.w(TAG, "linkProgram", "Could not create new program");
return programObjectId;
}
glAttachShader(programObjectId, vertexShaderId);
glAttachShader(programObjectId, fragmentShaderId);
glLinkProgram(programObjectId);
final int[] linkStatus = new int[1];
glGetProgramiv(programObjectId, GL_LINK_STATUS, linkStatus, 0);
if (linkStatus[0] == 0) {
glDeleteProgram(programObjectId);
VLog.w(TAG, "linkProgram", glGetProgramInfoLog(programObjectId));
return programObjectId;
}
return programObjectId;
}
public static boolean validateProgram(int programObjectId) {
//        if (!BuildConfig.DEBUG) {
//            return true;
//        }
glValidateProgram(programObjectId);
final int[] validateStatus = new int[1];
glGetProgramiv(programObjectId, GL_VALIDATE_STATUS, validateStatus, 0);
VLog.d("Results of validating program: ", new String[]{"validateStatus", "ProgramInfo"},
new String[]{String.valueOf(validateStatus[0]), glGetProgramInfoLog(programObjectId)});
return validateStatus[0] != 0;
}

triangle_vertex_shader

attribute vec4 vPosition;
void main() {
gl_Position = vPosition;
}

triangle_fragment_shader

precision mediump float;
uniform vec4 vColor;
void main() {
gl_FragColor = vColor;
}

Answer 1

经过细致的调查，我发现根本原因是我错误地提供了片段着色器作为顶点着色器。正确的格式如下:

mProgram = ShaderHelper.buildProgram(
TextResourceReader.readTextFileFromResource(
context,
R.raw.triangle_vertex_shader
),
TextResourceReader.readTextFileFromResource(
context,
R.raw.triangle_fragment_shader
)
)