我在互联网上找到了关于如何在opengl es 2.0中加载多个纹理的这段代码：
//
// Book: OpenGL(R) ES 2.0 Programming Guide
// Authors: Aaftab Munshi, Dan Ginsburg, Dave Shreiner
// ISBN-10: 0321502795
// ISBN-13: 9780321502797
// Publisher: Addison-Wesley Professional
// URLs: http://safari.informit.com/9780321563835
// http://www.opengles-book.com
//
// MultiTexture.c
//
// This is an example that draws a quad with a basemap and
// lightmap to demonstrate multitexturing.
//
#include"pch.h"
#include <stdlib.h>
typedef struct
{
// Handle to a program object
GLuint programObject;
// Attribute locations
GLint positionLoc;
GLint texCoordLoc;
// Sampler locations
GLint baseMapLoc;
GLint lightMapLoc;
// Texture handle
GLuint baseMapTexId;
GLuint lightMapTexId;
} UserData;
///
// Load texture from disk
//
GLuint LoadTexture(char *fileName)
{
int width,
height;
char *buffer = esLoadTGA(fileName, &width, &height);
GLuint texId;
if (buffer == NULL)
{
esLogMessage("Error loading (%s) image.\n", fileName);
return 0;
}
glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
free(buffer);
return texId;
}
///
// Initialize the shader and program object
//
int Init(ESContext *esContext)
{
UserData *userData = (UserData*) esContext->userData;
const char vShaderStr[] =
"attribute vec4 a_position; \n"
"attribute vec2 a_texCoord; \n"
"varying vec2 v_texCoord; \n"
"void main() \n"
"{ \n"
" gl_Position = a_position; \n"
" v_texCoord = a_texCoord; \n"
"} \n";
const char fShaderStr[] =
"precision mediump float; \n"
"varying vec2 v_texCoord; \n"
"uniform sampler2D s_baseMap; \n"
"uniform sampler2D s_lightMap; \n"
"void main() \n"
"{ \n"
" vec4 baseColor; \n"
" vec4 lightColor; \n"
" \n"
" baseColor = texture2D( s_baseMap, v_texCoord ); \n"
" lightColor = texture2D( s_lightMap, v_texCoord ); \n"
" gl_FragColor = baseColor * (lightColor + 0.25); \n"
"} \n";
// Load the shaders and get a linked program object
userData->programObject = esLoadProgram(vShaderStr, fShaderStr);
// Get the attribute locations
userData->positionLoc = glGetAttribLocation(userData->programObject, "a_position");
userData->texCoordLoc = glGetAttribLocation(userData->programObject, "a_texCoord");
// Get the sampler location
userData->baseMapLoc = glGetUniformLocation(userData->programObject, "s_baseMap");
userData->lightMapLoc = glGetUniformLocation(userData->programObject, "s_lightMap");
// Load the textures
userData->baseMapTexId = LoadTexture("basemap.tga");
userData->lightMapTexId = LoadTexture("lightmap.tga");
if (userData->baseMapTexId == 0 || userData->lightMapTexId == 0)
return FALSE;
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw(ESContext *esContext)
{
UserData *userData = (UserData*)esContext->userData;
GLfloat vVertices[] = { -0.5f, 0.5f, 0.0f, // Position 0
0.0f, 0.0f, // TexCoord 0
-0.5f, -0.5f, 0.0f, // Position 1
0.0f, 1.0f, // TexCoord 1
0.5f, -0.5f, 0.0f, // Position 2
1.0f, 1.0f, // TexCoord 2
0.5f, 0.5f, 0.0f, // Position 3
1.0f, 0.0f // TexCoord 3
};
GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
// Set the viewport
glViewport(0, 0, esContext->width, esContext->height);
// Clear the color buffer
glClear(GL_COLOR_BUFFER_BIT);
// Use the program object
glUseProgram(userData->programObject);
// Load the vertex position
glVertexAttribPointer(userData->positionLoc, 3, GL_FLOAT,
GL_FALSE, 5 * sizeof(GLfloat), vVertices);
// Load the texture coordinate
glVertexAttribPointer(userData->texCoordLoc, 2, GL_FLOAT,
GL_FALSE, 5 * sizeof(GLfloat), &vVertices[3]);
glEnableVertexAttribArray(userData->positionLoc);
glEnableVertexAttribArray(userData->texCoordLoc);
// Bind the base map
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, userData->baseMapTexId);
// Set the base map sampler to texture unit to 0
glUniform1i(userData->baseMapLoc, 0);
// Bind the light map
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, userData->lightMapTexId);
// Set the light map sampler to texture unit 1
glUniform1i(userData->lightMapLoc, 1);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface);
}
///
// Cleanup
//
void ShutDown(ESContext *esContext)
{
UserData *userData = (UserData*)esContext->userData;
// Delete texture object
glDeleteTextures(1, &userData->baseMapTexId);
glDeleteTextures(1, &userData->lightMapTexId);
// Delete program object
glDeleteProgram(userData->programObject);
}
int main(int argc, char *argv[])
{
ESContext esContext;
UserData userData;
esInitContext(&esContext);
esContext.userData = &userData;
esCreateWindow(&esContext, L"MultiTexture", 320, 240, ES_WINDOW_RGB);
if (!Init(&esContext))
return 0;
esRegisterDrawFunc(&esContext, Draw);
esMainLoop(&esContext);
ShutDown(&esContext);
}
但是当我运行它时它只显示黑暗！调试代码表明什么都不是null或者什么，那么它有什么问题呢？ 我添加两个名称与代码相同的文件，但我仍然看到一个黑暗的空间！ 有什么建议吗？ 另一个问题是这是加载任何数量纹理的常用方法吗？
答案 0 :(得分：0)
首先尝试绘制一个红色正方形（使用gl_FragColor = vec4（1.0,0.0,0.0,1.0））。如果没有绘制，则更改索引的顺序（您可能正常向后）。
第二，你需要在绘制之前将纹理提交给GPU。
在GPU有机会接管内存之前释放缓冲区（在使用该纹理绘制任何内容之前调用free（缓冲区），缓冲区还没有在GPU内存上）。
要提交纹理，请使用该纹理绘制内容。
以下是强制提交的示例代码（随意根据您的需求进行调整）：
void cColorTest::ForceCommitTexture(unsigned int texId)
{
glUseProgram(m_nProgram);
glBindTexture(GL_TEXTURE_2D,texId);
GLfloat triangle[]= { 0.0f, 0.5f, 0.5f, 1.0f, 1.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f};
glVertexAttribPointer ( m_nPosLoc, 4, GL_FLOAT, GL_FALSE, 6 * sizeof(float), triangle );
glEnableVertexAttribArray ( m_nPosLoc );
glVertexAttribPointer ( m_nUVLoc, 2, GL_FLOAT, GL_FALSE, 6 * sizeof(float), triangle + 4 );
glEnableVertexAttribArray ( m_nUVLoc );
glDrawArrays(GL_TRIANGLES,0,1);
}