c++ - 模型在窗口调整 OpenGL 3.2 大小时拉伸(stretch)

Question

我已经设置了一个包含 OpenGL 3.2 渲染上下文的窗口(在 MFC 中)。因为它与 OpenGL 3.2 一起使用，所以我想使用着色器等，所以我手动构建投影和 View 矩阵。我用过 this教程作为构建它们并将它们传递给我的着色器的输入。

现在的问题是(即使在教程的示例中)当我调整窗口大小时，模型被拉伸(stretch)。

这是我用来构建矩阵的代码(我重建它们并在每次刷新窗口时将它们发送到我的着色器)。

查看矩阵:

float zAxis[3], xAxis[3], yAxis[3]; 
float length, result1, result2, result3;

// zAxis = normal(lookAt - position)
zAxis[0] = lookAt[0] - m_position[0];
zAxis[1] = lookAt[1] - m_position[1];
zAxis[2] = lookAt[2] - m_position[2];
length = sqrt((zAxis[0] * zAxis[0]) + (zAxis[1] * zAxis[1]) + (zAxis[2] * zAxis[2]));
zAxis[0] = zAxis[0] / length;
zAxis[1] = zAxis[1] / length;
zAxis[2] = zAxis[2] / length;

// xAxis = normal(cross(up, zAxis))
xAxis[0] = (up[1] * zAxis[2]) - (up[2] * zAxis[1]);
xAxis[1] = (up[2] * zAxis[0]) - (up[0] * zAxis[2]);
xAxis[2] = (up[0] * zAxis[1]) - (up[1] * zAxis[0]);
length = sqrt((xAxis[0] * xAxis[0]) + (xAxis[1] * xAxis[1]) + (xAxis[2] * xAxis[2]));
xAxis[0] = xAxis[0] / length;
xAxis[1] = xAxis[1] / length;
xAxis[2] = xAxis[2] / length;

// yAxis = cross(zAxis, xAxis)
yAxis[0] = (zAxis[1] * xAxis[2]) - (zAxis[2] * xAxis[1]);
yAxis[1] = (zAxis[2] * xAxis[0]) - (zAxis[0] * xAxis[2]);
yAxis[2] = (zAxis[0] * xAxis[1]) - (zAxis[1] * xAxis[0]);

// -dot(xAxis, position)
result1 = ((xAxis[0] * m_position[0]) + (xAxis[1] * m_position[1]) + (xAxis[2] * m_position[2])) * -1.0f;

// -dot(yaxis, eye)
result2 = ((yAxis[0] * m_position[0]) + (yAxis[1] * m_position[1]) + (yAxis[2] * m_position[2])) * -1.0f;

// -dot(zaxis, eye)
result3 = ((zAxis[0] * m_position[0]) + (zAxis[1] * m_position[1]) + (zAxis[2] * m_position[2])) * -1.0f;

viewMatrix[0]  = xAxis[0];
viewMatrix[1]  = yAxis[0];
viewMatrix[2]  = zAxis[0];
viewMatrix[3]  = 0.0f;

viewMatrix[4]  = xAxis[1];
viewMatrix[5]  = yAxis[1];
viewMatrix[6]  = zAxis[1];
viewMatrix[7]  = 0.0f;

viewMatrix[8]  = xAxis[2];
viewMatrix[9]  = yAxis[2];
viewMatrix[10] = zAxis[2];
viewMatrix[11] = 0.0f;

viewMatrix[12] = result1;
viewMatrix[13] = result2;
viewMatrix[14] = result3;
viewMatrix[15] = 1.0f;

投影矩阵:

float screenAspect = (float)rcClient.Width() / (float)rcClient.Height();
float fov = 3.14159265358979323846f / 4.0f;
float zfar = 1000.0;
float znear = 0.1f;

projectionMatrix[0]  = 1.0f / (screenAspect * tan( fov * 0.5f));
projectionMatrix[1]  = 0.0f;
projectionMatrix[2]  = 0.0f;
projectionMatrix[3]  = 0.0f;

projectionMatrix[4]  = 0.0f;
projectionMatrix[5]  = 1.0f / tan( fov * 0.5f);
projectionMatrix[6]  = 0.0f;
projectionMatrix[7]  = 0.0f;

projectionMatrix[8]  = 0.0f;
projectionMatrix[9]  = 0.0f;
projectionMatrix[10] = zfar / (zfar - znear);
projectionMatrix[11] = 1.0f;

projectionMatrix[12] = 0.0f;
projectionMatrix[13] = 0.0f;
projectionMatrix[14] = (-znear * zfar) / (zfar - znear);
projectionMatrix[15] = 0.0f;

在我的着色器中，我这样使用它们:

#version 150

in vec3 inputPosition;
in vec3 inputColor;

out vec3 color;

uniform mat4 worldMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;

void main(void)
{
    gl_Position = projectionMatrix * viewMatrix * worldMatrix * vec4(inputPosition, 1.0f);

    color = inputColor;
}

有人知道这里发生了什么吗？

Answer 1

不要使用 glViewport，因为您可以只使用着色器，这是首选方式。

你能把你的投影矩阵改成:

float projectionMatrix[4][4];
projectionMatrix[0][0]  = 1.0f / (screenAspect * tan( fov * 0.5f));
projectionMatrix[0][1]  = 0.0f;
projectionMatrix[0][2]  = 0.0f;
projectionMatrix[0][3]  = 0.0f;

projectionMatrix[1][0]  = 0.0f;
projectionMatrix[1][1]  = 1.0f / tan( fov * 0.5f);
projectionMatrix[1][2]  = 0.0f;
projectionMatrix[1][3]  = 0.0f;

projectionMatrix[2][0]  = 0.0f;
projectionMatrix[2][1]  = 0.0f;
projectionMatrix[2][2] = (-znear -zfar) / (znear-zfar);
projectionMatrix[2][3] = 2.0f * zfar * znear / (znear-zfar);

projectionMatrix[3][0] = 0.0f;
projectionMatrix[3][1] = 0.0f;
projectionMatrix[3][2] = 1.0;
projectionMatrix[3][3] = 0.0f;

我不确定你的 UVN 矩阵，但它可能不是问题，因为你在使用 glViewport 后它开始工作了。无论如何，您可以使用 GLM 而不是生成矩阵。此处给出了构建投影、UVN、平移矩阵等的代码示例:glm code example我认为本教程对转换的解释足够好:http://ogldev.atspace.co.uk/