OpenGL比例三角形网格到单位立方体

时间:2018-11-25 06:49:46

标签: c++ opengl scaling coordinate-transformation

我正在尝试从.off文件加载三角形网格,并显示以原点为中心并缩放以适合单位立方体的三角形网格。但是由于某种原因,我离开的原因很大,看起来

enter image description here

我这样做的方法是找到网格的极值,并使用该极值使曲面偏移该数量。

float avgX = (maxX + minX) / 2;
float avgY = (maxY + minY) / 2;
float avgZ = (maxZ + minZ) / 2;
Vector3f center(avgX, avgY, avgZ);
Vector3f offset = Vector3f(0, 0, 0) - center;
Translation3f translation(offset);

cout << "offset is: " << endl << offset << endl;

double d_theta = (M_PI / 180);
AngleAxisf rotation(d_theta, Vector3f(0, 0, 1));

float scaleX = (float) 1 / (abs(maxX - minX));
float scaleY = (float) 1 / (abs(maxY - minY));
float scaleZ = (float) 1 / (abs(maxZ - minZ));
AlignedScaling3f scale = AlignedScaling3f(scaleX, scaleY, scaleZ);

然后我将其放入具有以下特征的表面向量中

Vector3f translatedCenter = translation * rotation * scale * center;

VertexBufferObject VBO;
VBO.init();
VBO.update(Vertices);
program.bindVertexAttribArray("position", VBO);

VertexBufferObject VBO_N;
VBO_N.init();
VBO_N.update(FlatNormals);
program.bindVertexAttribArray("normals", VBO_N);

cout << "updated normals" << endl;

VertexBufferObject VBO_C;
VBO_C.init();
VBO_C.update(C);
program.bindVertexAttribArray("color",VBO_C);

cout << "updated color " << endl;

Surface* s = new Surface(VBO, Vertices, translation, rotation, scale, percentScale, translatedCenter, SmoothNormals, FlatNormals, C);

然后将其作为“模型”传递给Vertex Shader

Affine3f model = s->getTranslation() * s->getRotation() * s->getScale();
glUniformMatrix4fv(program.uniform("model"), 1, GL_FALSE, model.data()); 

这一切都使用特征库(https://eigen.tuxfamily.org/dox/group__TutorialGeometry.html#TutorialGeoTransform

完成

不管我尝试什么,我都会一点点离开。我在做什么错了?

1 个答案:

答案 0 :(得分:1)

交换平移和旋转:

 Affine3f model = s->getRotation() * s->getTranslation() * s->getScale();

请注意,平移会将对象的中心移动到视图的中心。之后,旋转矩阵围绕此中心旋转。

如果没有任何投影矩阵,则视图空间是归一化的设备空间,其中每个坐标都在[-1,1]范围内。这意味着边的长度为2 = 1 - (-1)。在计算比例时必须遵守这一点:

float scaleX = (float) 2 / (abs(maxX - minX));
float scaleY = (float) 2 / (abs(maxY - minY));
float scaleZ = (float) 2 / (abs(maxZ - minZ));