OpenGL 是否将屏幕定位在相机前？

如何解决OpenGL 是否将屏幕定位在相机前？

我正在尝试将鼠标点击转换为全局位置。尽管世界空间是 3d，我目前正在尝试找到 z = 0 处点击的 x 和 y 坐标。

我已经写了一些进行转换的代码，它几乎是正确的。但似乎有一个误差随着距 (0,0) 的距离而增长。它似乎增长得太快，是一个舍入错误，所以我认为屏幕没有设置到相机位置。

对于这个测试，我专注于 x 坐标。

变量

screenWidth = 512;
screenHeight = 512;
cameraPos = glm::vec3(0.0f,0.0f,4.0f);

转换逻辑

    std::cout << "mouse float x: " << inMouseX << ",mouse float y: " << inMouseY << std::endl;


    float mouseX = (inMouseX / ((float)screenWidth * 0.5f)) - 1.0f;
    float mouseY = (inMouseY / ((float)screenHeight * 0.5f)) - 1.0f;

    std::cout << "mouse adjusted screen width x: " << (float)screenWidth * 0.5f << ",mouse adjusted screen height y: " << (float)screenHeight * 0.5f << std::endl;
    std::cout << "mouse 2nd adjusted x: " << ((inMouseX / (float)screenWidth * 0.5f)) << ",mouse 2nd adjusted y: " << ((inMouseY / (float)screenHeight * 0.5f)) << std::endl;

    std::cout << "mouse converted x: " << mouseX << ",mouse converted y: " << mouseY << std::endl;

    glm::mat4 invVP = glm::inverse(*projection * *view);

    glm::vec4 mouseClickVector = invVP * glm::vec4(mouseX,-mouseY,1.0f,1.0f);

    glm::vec3 norm = glm::normalize(glm::vec3(mouseClickVector));

    float t = (0 - (*cameraPos)[2]) / norm[2];

    glm::vec3 trueWorldPos = *cameraPos + (norm * t);

    return trueWorldPos;

示例响应

------------case 1------------
expected:
mouse world position x: 0

actual:
mouse float x: 256,mouse float y: 255
mouse adjusted screen width x: 256,mouse adjusted screen height y: 256
mouse 2nd adjusted x: 0.25,mouse 2nd adjusted y: 0.249023
mouse converted x: 0,mouse converted y: -0.00390625
mouse world position x: 0,mouse world y: 0.0162761

------------case 2------------
expected:
mouse world position x: 5

actual:
mouse float x: 189,mouse float y: 251
mouse adjusted screen width x: 256,mouse adjusted screen height y: 256
mouse 2nd adjusted x: 0.18457,mouse 2nd adjusted y: 0.245117
mouse converted x: -0.261719,mouse converted y: -0.0195313
mouse world position x: 5.23121,mouse world y: 0.0813803

------------case 3------------
expected:
mouse world position x: 7

actual:
mouse float x: 82,mouse float y: 254
mouse adjusted screen width x: 256,mouse adjusted screen height y: 256
mouse 2nd adjusted x: 0.0800781,mouse 2nd adjusted y: 0.248047
mouse converted x: -0.679688,mouse converted y: -0.0078125
mouse world position x: 7.25648,mouse world y: 0.0325521

我预计会有一些波动，因为我使用鼠标不精确，可能还有一些小的舍入问题，但它比我预期的要大得多。

解决方法

假设视图矩阵有一些标准约定，这是没有意义的：

<#if transaction.custbody72 == "T">

通常，视图矩阵包含相机的方向和位置。您似乎将 glm::vec4 mouseClickVector = invVP * glm::vec4(mouseX,-mouseY,1.0f,1.0f); glm::vec3 norm = glm::normalize(glm::vec3(mouseClickVector)); 视为一个方向。但如果您的相机不在世界空间中心，这种标准化将产生完全虚假的结果。

要获得未投影点的正确世界空间位置，您不能再忽略 w 组件：

mouseClickVector

那只会在背板上产生未投影的点（当您将 NDC z 设置为 1.0 时）。您仍然需要计算从相机位置到该点的视图射线，以便您可以计算与某个世界空间平面的交点。