OpenGL混合在纹理周围创建白色边框

Question

我正在尝试使用OpenGL(C++)将两个纹理渲染到一个矩形上.虽然我在混合他们两个时遇到了一些麻烦.

第一张图片来自.jpg文件(https://learnopengl.com/img/textures/container.jpg).此图片没有Alpha通道.

第二张图片来自.png文件(https://learnopengl.com/img/textures/awesomeface.png),并且有一个alpha通道.

问题是当我尝试混合两个图像时,它会在透明图像周围创建一个白色边框.

我已经尝试了一些不同的混合模式(在这个问题中OP的推荐:Alpha混合多个纹理留下彩色边框)但它们似乎都不起作用.

我的片段着色器看起来像这样:

#version 330 core
out vec4 FragColor;

in vec3 ourColor;
in vec2 TexCoord;

// texture samplers
uniform sampler2D texture1;
uniform sampler2D texture2;

void main()
{
    // linearly interpolate between both textures
    FragColor = mix(texture(texture1, TexCoord), texture(texture2, TexCoord), 0.5);
}

我启用了深度测试(似乎没有任何效果),我正在使用以下代码来设置我的混合:

glEnable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

这是我的主渲染循环:

Rendering::Pipeline pipeline = Rendering::Pipeline("src/GLSL/vertex.glsl", "src/GLSL/fragment.glsl");
pipeline.load();

//                     Position,               Color,                   Texture Coord.
//                     (X Y Z)                 (R G B)                  (S T)
float vertices [32] = { 0.5f,   0.5f,   0.0f,   1.0f,   0.0f,   0.0f,   1.0f, 1.0f, // top right
                        0.5f,   -0.5f,  0.0f,   0.0f,   1.0f,   0.0f,   1.0f, 0.0f, // bottom right
                        -0.5f,  -0.5f,  0.0f,   0.0f,   0.0f,   1.0f,   0.0f, 0.0f, // bottom left
                        -0.5f,  0.5f,   0.0f,   1.0f,   1.0f,   0.0f,   0.0f, 1.0f  };// top left

unsigned int vertexIndices [6] = {  3,  2,  0,
                                    2,  1,  0   };


unsigned int vbo;
unsigned int vao;
unsigned int ebo;

glGenVertexArrays(1, &vao);
glGenBuffers(1, &vbo);
glGenBuffers(1, &ebo);

glBindVertexArray(vao);

glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(vertexIndices), vertexIndices, GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*) 0);
glEnableVertexAttribArray(0);

glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*) (3 * sizeof(float)));
glEnableVertexAttribArray(1);

glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*) (6 * sizeof(float)));
glEnableVertexAttribArray(2);

unsigned int texture1;
unsigned int texture2;
int width;
int height;
int numChannels;
unsigned char* data;

glGenTextures(1, &texture1);
glBindTexture(GL_TEXTURE_2D, texture1);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

data = stbi_load("res/jpg/container.jpg", &width, &height, &numChannels, STBI_rgb);

if (data)
{
    lTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
}

stbi_image_free(data);

glGenTextures(1, &texture2);
glBindTexture(GL_TEXTURE_2D, texture2);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

stbi_set_flip_vertically_on_load(true);

data = stbi_load("res/png/awesomeface.png", &width, &height, &numChannels, STBI_rgb_alpha);

if (data)
{
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
}

stbi_image_free(data);

glUseProgram(pipeline.getProgramId());
glUniform1i(glGetUniformLocation(pipeline.getProgramId(), "texture1"), 0);
glUniform1i(glGetUniformLocation(pipeline.getProgramId(), "texture2"), 1);

while (!this->mQuit)
{
    this->counter.start();

    InputProcessor::getInstance().processInputs();

    if (this->debugOverlay)
    {
        glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    }
    else
    {
        glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
    }

    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture1);

    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, texture2);

    pipeline.use();
    glBindVertexArray(vao);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

    SDL_GL_SwapWindow(this->sdlWindow);

    this->counter.stop();
    this->deltaTime = this->counter.getDelta();
}

    this->quit();

将0.5作为参数传递给片段着色器中的mix()函数时,最容易发现该问题.当使用0.0或1.0时,我得到(如预期)只有一个纹理.

Answer 1

问题可能出在纹理本身。如果您探测边界附近被 alpha 取消的像素处的半透明纹理，RGB 值是多少？有些编辑器（Photoshop深度）用白色（或默认颜色）填充透明区域，这可能会在混合过程中产生这些边框。

抗锯齿或插值会导致白色渗入可见区域。

我没有从软件开发人员的角度来处理这个问题，但作为内容创建者，我不止一次地被这个问题所困扰（例如，这是《第二人生》中新手的祸害）。