先一发流程图：
重点流程
1、编译Shader代码
/**
* 编译着色器
*/
private fun compileShader(type: Int, shaderSourceCode: String): Int {
//1、创建Shader
val shaderObjectId = glCreateShader(type)
if (shaderObjectId == 0) {
LOGE(msg = "create shader failed!")
return 0
}
//2、shader和GDLS代码关联
glShaderSource(shaderObjectId, shaderSourceCode)
//3、编译shader
glCompileShader(shaderObjectId)
//4、验证编译结果
val compileStatus = IntArray(1)
//glGetShaderiv函数比较通用，在着色器阶段和 OpenGL 程序阶段都会通过它来验证结果。
glGetShaderiv(shaderObjectId, GL_COMPILE_STATUS, compileStatus, 0)
if ((compileStatus[0] == 0)) {
// 失败则删除
glDeleteShader(shaderObjectId)
LOGE(msg = "compileShader failed!, type=$type")
return 0
}
return shaderObjectId
}
2、链接着色器
/**
* 创建 着色器 程序和着色器链接
* @param vertexShaderId 通过[compileShader]创建的shader对象
* @param fragmentShaderId 通过[compileShader]创建的shader对象
*/
fun linkProgram(vertexShaderId: Int, fragmentShaderId: Int): Int {
//1、创建OpenGL程序
val programObjectId = glCreateProgram()
//2、链接shader
glAttachShader(programObjectId, vertexShaderId)
glAttachShader(programObjectId, fragmentShaderId)
//3、链接OpenGL程序
glLinkProgram(programObjectId)
//4、验证链接结果
val linkStatus = IntArray(1)
glGetProgramiv(programObjectId, GL_LINK_STATUS, linkStatus, 0)
if ((linkStatus[0] == 0)) {
LOGI(
msg =
"""
Result of linking program:
${glGetProgramInfoLog(programObjectId)}
""".trimIndent()
)
// 失败则删除
glDeleteProgram(programObjectId)
LOGE(msg = "link program failed!")
return 0
}
return programObjectId
}
3、链接顶点属性
/**
* 使顶点某个数据使能的
* @param dataOffset
* @param attributeLocation
* @param componentCount
* @param stride
*/
fun setVertexAttribPointer(
dataOffset: Int,
attributeLocation: Int,
componentCount: Int,
stride: Int
) {
floatBuffer.position(dataOffset)
GLES20.glVertexAttribPointer(
attributeLocation,
componentCount,
GLES20.GL_FLOAT,
false,
stride,
floatBuffer
)
GLES20.glEnableVertexAttribArray(attributeLocation)
floatBuffer.position(0)
}
val floatBuffer: FloatBuffer = ByteBuffer
.allocateDirect(vertexData.size * Constants.BYTES_PRE_FLOAT)
.order(ByteOrder.nativeOrder())
.asFloatBuffer()
.put(vertexData)
