OpenGL 画出雷达动态扫描效果(二) 非底图

非底图雷达动态扫描效果可以通过OpenGL的绘制方式来实现。具体实现可以参考以下步骤：

1. 设置OpenGL视口和投影矩阵，使雷达扫描区域位于屏幕中心部位。

2. 在OpenGL中创建一个圆形网格，用于表示雷达扫描区域。

3. 创建一个纹理，用于表示雷达扫描的反射强度。可以根据实际需要，选择不同的纹理生成算法。

4. 在OpenGL中创建一个圆锥体，用于表示雷达扫描的扫描区域。

5. 将圆锥体与圆形网格进行裁剪，得到雷达扫描区域的可见部分。

6. 将可见部分与纹理进行融合，得到最终的雷达扫描效果。

实现过程中，可以使用OpenGL的渲染管线来实现雷达扫描效果。具体实现可以参考以下代码：

// 设置视口和投影矩阵
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-1, 1, -1, 1);

// 创建圆形网格
int numSegments = 32;
float radius = 0.8;
float* vertices = new float[(numSegments + 1) * 2];
for (int i = 0; i <= numSegments; i++) {
    float angle = i * 2.0f * M_PI / numSegments;
    vertices[i * 2] = radius * cosf(angle);
    vertices[i * 2 + 1] = radius * sinf(angle);
}
unsigned int* indices = new unsigned int[numSegments * 2];
for (int i = 0; i < numSegments; i++) {
    indices[i * 2] = i;
    indices[i * 2 + 1] = i + 1;
}
unsigned int vao, vbo, ibo;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, (numSegments + 1) * 2 * sizeof(float), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glGenBuffers(1, &ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, numSegments * 2 * sizeof(unsigned int), indices, GL_STATIC_DRAW);

// 创建纹理
int textureWidth = 256;
int textureHeight = 256;
unsigned char* textureData = new unsigned char[textureWidth * textureHeight];
for (int i = 0; i < textureHeight; i++) {
    for (int j = 0; j < textureWidth; j++) {
        float distance = sqrtf((float)(i - textureHeight / 2) * (i - textureHeight / 2) + (float)(j - textureWidth / 2) * (j - textureWidth / 2));
        float intensity = 1.0f - distance / (textureWidth / 2);
        intensity = intensity < 0.0f ? 0.0f : intensity;
        textureData[i * textureWidth + j] = (unsigned char)(intensity * 255);
    }
}
unsigned int texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, textureWidth, textureHeight, 0, GL_RED, GL_UNSIGNED_BYTE, textureData);
glBindTexture(GL_TEXTURE_2D, 0);

// 创建圆锥体
int numSlices = 16;
float coneHeight = 0.5;
float* coneVertices = new float[(numSegments + 1) * 3 + (numSegments + 1) * 3];
for (int i = 0; i <= numSegments; i++) {
    float angle = i * 2.0f * M_PI / numSegments;
    coneVertices[i * 3] = vertices[i * 2];
    coneVertices[i * 3 + 1] = vertices[i * 2 + 1];
    coneVertices[i * 3 + 2] = 0;
    coneVertices[(numSegments + 1) * 3 + i * 3] = vertices[i * 2] * coneHeight;
    coneVertices[(numSegments + 1) * 3 + i * 3 + 1] = vertices[i * 2 + 1] * coneHeight;
    coneVertices[(numSegments + 1) * 3 + i * 3 + 2] = coneHeight;
}
unsigned int* coneIndices = new unsigned int[numSlices * 3];
for (int i = 0; i < numSlices; i++) {
    coneIndices[i * 3] = i;
    coneIndices[i * 3 + 1] = (i + 1) % numSegments;
    coneIndices[i * 3 + 2] = numSegments;
}
unsigned int coneVao, coneVbo, coneIbo;
glGenVertexArrays(1, &coneVao);
glBindVertexArray(coneVao);
glGenBuffers(1, &coneVbo);
glBindBuffer(GL_ARRAY_BUFFER, coneVbo);
glBufferData(GL_ARRAY_BUFFER, (numSegments + 1) * 3 * 2 * sizeof(float), coneVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glGenBuffers(1, &coneIbo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, coneIbo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, numSlices * 3 * sizeof(unsigned int), coneIndices, GL_STATIC_DRAW);

// 绘制雷达扫描
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
for (float angle = 0; angle < 360; angle += 8) {
    glLoadIdentity();
    glRotatef(angle, 0, 0, 1);
    glBindVertexArray(vao);
    glDrawElements(GL_LINES, numSegments * 2, GL_UNSIGNED_INT, 0);
    glBindVertexArray(coneVao);
    glDrawElements(GL_TRIANGLES, numSlices * 3, GL_UNSIGNED_INT, 0);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_ALPHA_TEST);
    glAlphaFunc(GL_GREATER, 0.1f);
    glEnable(GL_CLIP_DISTANCE0);
    float plane[4] = { 0, 0, -1, 0 };
    glClipPlane(GL_CLIP_DISTANCE0, plane);
    glDrawElements(GL_TRIANGLES, numSlices * 3, GL_UNSIGNED_INT, 0);
    glDisable(GL_CLIP_DISTANCE0);
    glDisable(GL_ALPHA_TEST);
    glDisable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);
}
glDisable(GL_BLEND);

在上述代码中，使用OpenGL的渲染管线和纹理，实现了非底图雷达动态扫描效果。通过调整圆形网格、圆锥体和纹理的参数，可以实现不同形状、不同大小、不同反射强度的雷达扫描效果。