我有以下问题:
这是我在屏幕上绘制多维数据集的方式:
void drawCube()
{
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear color and depth buffers
glPushAttrib(GL_POLYGON_BIT | GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT) ;
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE) ;
//glDisable(GL_LIGHTING) ;
glBegin(GL_QUADS); // Begin drawing the color cube with size 3cm x 3.5cm x 4cm
// Top face (y = 1.0f)
// Define vertices in counter-clockwise (CCW) order with normal pointing out
glColor3f(0.0f, 1.0f, 0.0f); // Green
glVertex3f( 1.75f, 1.75f, -4.0f);
glVertex3f(-1.75f, 1.75f, -4.0f);
glVertex3f(-1.75f, 1.75f, 1.0f);
glVertex3f( 1.75f, 1.75f, 1.0f);
// Bottom face (y = -1.0f)
glColor3f(1.0f, 0.5f, 0.0f); // Orange
glVertex3f( 1.75f, -1.75f, 1.0f);
glVertex3f(-1.75f, -1.75f, 1.0f);
glVertex3f(-1.75f, -1.75f, -4.0f);
glVertex3f( 1.75f, -1.75f, -4.0f);
// Front face (z = 1.0f)
glColor3f(1.0f, 0.0f, 0.0f); // Red
glVertex3f( 1.75f, 1.75f, 1.0f);
glVertex3f(-1.75f, 1.75f, 1.0f);
glVertex3f(-1.75f, -1.75f, 1.0f);
glVertex3f( 1.75f, -1.75f, 1.0f);
// Back face (z = -1.0f)
glColor3f(1.0f, 1.0f, 0.0f); // Yellow
glVertex3f( 1.75f, -1.75f, -4.0f);
glVertex3f(-1.75f, -1.75f, -4.0f);
glVertex3f(-1.75f, 1.75f, -4.0f);
glVertex3f( 1.75f, 1.75f, -4.0f);
// Left face (x = -1.0f)
glColor3f(0.0f, 0.0f, 1.0f); // Blue
glVertex3f(-1.75f, 1.75f, 1.0f);
glVertex3f(-1.75f, 1.75f, -4.0f);
glVertex3f(-1.75f, -1.75f, -4.0f);
glVertex3f(-1.75f, -1.75f, 1.0f);
// Right face (x = 1.0f)
glColor3f(1.0f, 0.0f, 1.0f); // Magenta
glVertex3f(1.75f, 1.75f, -4.0f);
glVertex3f(1.75f, 1.75f, 1.0f);
glVertex3f(1.75f, -1.75f, 1.0f);
glVertex3f(1.75f, -1.75f, -4.0f);
glEnd(); // End of drawing color-cube
glPopAttrib() ;
}
问题是如何在所有顶点之间分配“采样点”？
根据我的理解，我需要找到顶点之间的距离并将其分为(例如)五个相等的部分。为了便于讨论，假设两个顶点之间的间隔为1，那么将5个点放置在彼此相距0.2的距离上。另外，还需要将它们存储为一种内存结构( vector /数组)，以便可以在以后的每个阶段访问它们并将其转换为屏幕坐标。
但是，我该如何以完全通用的方式在C++中做到这一点，以便基本上可以将其应用于任何距离度量？
Here is how the cube looks like
最佳答案
这是我的drawBox函数，如果需要，您可以对其进行修改以在每个面上绘制不同的颜色。
void DrawBox(GLfloat fWidth,GLfloat fHeight,GLfloat fDepth,GLint wslices,GLint dslices,GLint stacks)
{
// Calculate number of primitives on each side of box
// because we can use different tessalation configurations
// we must calculate separate group of box sides
int iTopButtonQuads = wslices * dslices * 2; // Calculate number of quads in top and button sides
int iLeftRightQuads = dslices * stacks * 2; // Calculate number of quads in left and right sides
int iFrontBackQuads = wslices * stacks * 2; // Calculate number of quads in front and back sides
// If we consider to use quads as primitive then each primitive will
// have 4 points, and each point has color, coord and normal attribute.
// So we create separate array to contain each attibute values.
float* pfVertices = new float[(iTopButtonQuads + iLeftRightQuads + iFrontBackQuads) * 3 * 4];
float* pfColors = new float[(iTopButtonQuads + iLeftRightQuads + iFrontBackQuads) * 3 * 4];
float* pfNormals = new float[(iTopButtonQuads + iLeftRightQuads + iFrontBackQuads) * 3 * 4];
int iVertexIndex = 0;
GLfloat Xstep = fWidth / wslices;
GLfloat Ystep = fHeight / stacks;
GLfloat Zstep = fDepth / dslices;
GLfloat firstX = fWidth / 2.0f;
GLfloat firstY = fHeight / 2.0f;
GLfloat firstZ = fDepth / 2.0f;
GLfloat currX = 0.0f;
GLfloat currY = 0.0f;
GLfloat currZ = 0.0f;
GLfloat x_status = 0.0f;
GLfloat y_status = 0.0f;
GLfloat z_status = 0.0f;
// the bottom and the top of the box
for (currZ = -firstZ, z_status = 0.0f; currZ < firstZ - Zstep / 2.0f; currZ += Zstep, z_status += Zstep)
{
for (currX = -firstX, x_status = 0.0f; currX < firstX - Xstep / 2.0f; currX += Xstep, x_status += Xstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { 0.0f, -1.0f, 0.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 1.0f, 0.0f, 0.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {currX,-firstY,currZ};
float pfVertex1[3] = {currX + Xstep,-firstY,currZ};
float pfVertex2[3] = {currX + Xstep,-firstY,currZ + Zstep};
float pfVertex3[3] = {currX,-firstY,currZ + Zstep};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
for (currX = -firstX, x_status = 0.0f; currX < firstX - Xstep / 2.0f; currX += Xstep, x_status += Xstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { 0.0f, 1.0f, 0.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 0.0f, 1.0f, 0.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {currX + Xstep,firstY,currZ + Zstep};
float pfVertex1[3] = {currX + Xstep,firstY,currZ};
float pfVertex2[3] = {currX,firstY,currZ};
float pfVertex3[3] = {currX,firstY,currZ + Zstep};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
}
// the front and the back of the box
for (currY = -firstY, y_status = 0.0f; currY < firstY - Ystep / 2.0f ; currY += Ystep, y_status += Ystep)
{
for (currX = -firstX, x_status = 0.0f; currX < firstX - Xstep / 2.0f; currX += Xstep, x_status += Xstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { 0.0f, 0.0f, 1.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 0.0f, 0.0f, 1.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {currX,currY,firstZ};
float pfVertex1[3] = {currX + Xstep,currY,firstZ};
float pfVertex2[3] = {currX + Xstep,currY + Ystep,firstZ};
float pfVertex3[3] = {currX,currY + Ystep,firstZ};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
for (currX = -firstX, x_status = 0.0f; currX < firstX - Xstep / 2.0f; currX += Xstep, x_status += Xstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { 0.0f, 0.0f, -1.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 0.0f, 1.0f, 1.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {currX + Xstep,currY + Ystep,-firstZ};
float pfVertex1[3] = {currX + Xstep,currY,-firstZ};
float pfVertex2[3] = {currX,currY,-firstZ};
float pfVertex3[3] = {currX,currY + Ystep,-firstZ};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
}
// Right side and the left side of the box
for (currY = -firstY, y_status = 0.0f; currY < firstY - Ystep / 2.0f; currY += Ystep, y_status += Ystep)
{
for (currZ = -firstZ, z_status = 0.0f; currZ < firstZ - Zstep / 2.0f; currZ += Zstep, z_status += Zstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { 1.0f, 0.0f, 0.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 1.0f, 0.0f, 1.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {firstX,currY,currZ};
float pfVertex1[3] = {firstX,currY + Ystep,currZ};
float pfVertex2[3] = {firstX,currY + Ystep,currZ + Zstep};
float pfVertex3[3] = {firstX,currY,currZ + Zstep};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
for (currZ = -firstZ, z_status = 0.0f; currZ < firstZ - Zstep / 2.0f; currZ += Zstep, z_status += Zstep)
{
int iCurrentIndex = iVertexIndex * 3 * 4;
float pfNormal[3] = { -1.0f, 0.0f, 0.0f };
memcpy(pfNormals + iCurrentIndex, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 3, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 6, pfNormal, 3 * 4);
memcpy(pfNormals + iCurrentIndex + 9, pfNormal, 3 * 4);
float pfColor[3] = { 1.0f, 1.0f, 0.0f };
memcpy(pfColors + iCurrentIndex, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 3, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 6, pfColor, 3 * 4);
memcpy(pfColors + iCurrentIndex + 9, pfColor, 3 * 4);
float pfVertex0[3] = {-firstX,currY,currZ};
float pfVertex1[3] = {-firstX,currY,currZ + Zstep};
float pfVertex2[3] = {-firstX,currY + Ystep,currZ + Zstep};
float pfVertex3[3] = {-firstX,currY + Ystep,currZ};
memcpy(pfVertices + iCurrentIndex, pfVertex0, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 3, pfVertex1, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 6, pfVertex2, 3 * 4);
memcpy(pfVertices + iCurrentIndex + 9, pfVertex3, 3 * 4);
iVertexIndex++;
}
}
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glColorPointer(3, GL_FLOAT, 0, (void*)pfColors);
glNormalPointer(GL_FLOAT, 0, (void*)pfNormals);
glVertexPointer(3, GL_FLOAT, 0, (void*)pfVertices);
glDrawArrays(GL_QUADS, 0, (iTopButtonQuads + iLeftRightQuads + iFrontBackQuads) * 4);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
delete [] pfVertices;
delete [] pfNormals;
delete [] pfColors;
}
结果会像
这是用法创建的数组的示例，用于收集一些形状统计信息
// Example
// Find min-max of shapes coordinates
// Get coord of first vertex
float fMinX = pfVertices[0];
float fMinY = pfVertices[1];
float fMinZ = pfVertices[2];
float fMaxX = pfVertices[0];
float fMaxY = pfVertices[1];
float fMaxZ = pfVertices[2];
for (int iVertexIndex = 0; iVertexIndex < (iTopButtonQuads + iLeftRightQuads + iFrontBackQuads) * 4; iVertexIndex++)
{
int iCurrentIndex = iVertexIndex * 3; // (x y z) per vertex
if (pfVertices[iCurrentIndex] < fMinX)
fMinX = pfVertices[iCurrentIndex];
if (pfVertices[iCurrentIndex + 1] < fMinY)
fMinY = pfVertices[iCurrentIndex + 1];
if (pfVertices[iCurrentIndex + 2] < fMinZ)
fMinZ = pfVertices[iCurrentIndex + 2];
if (pfVertices[iCurrentIndex] > fMaxX)
fMaxX = pfVertices[iCurrentIndex];
if (pfVertices[iCurrentIndex + 1] > fMaxY)
fMaxY = pfVertices[iCurrentIndex + 1];
if (pfVertices[iCurrentIndex + 2] > fMaxZ)
fMaxZ = pfVertices[iCurrentIndex + 2];
}
// Create an axes aligned bounding box
// by simply drawing inflated min-maxes, that we collect
// example of using indexed primitives
glDisable(GL_CULL_FACE);
GLfloat vertices[] = {
fMinX - 2.0, fMaxY + 2.0, fMaxZ + 2.0,
fMaxX + 2.0, fMaxY + 2.0, fMaxZ + 2.0,
fMaxX + 2.0, fMinY - 2.0, fMaxZ + 2.0,
fMinX - 2.0, fMinY - 2.0, fMaxZ + 2.0,
fMinX - 2.0, fMaxY + 2.0, fMinZ - 2.0,
fMaxX + 2.0, fMaxY + 2.0, fMinZ - 2.0,
fMaxX + 2.0, fMinY - 2.0, fMinZ - 2.0,
fMinX - 2.0, fMinY - 2.0, fMinZ - 2.0
};
GLint indices[] = {
0, 1, 2, 3,
4, 5, 1, 0,
3, 2, 6, 7,
5, 4, 7, 6,
1, 5, 6, 2,
4, 0, 3, 7
};
glColor3f(1.0f, 1.0f, 1.0f);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, (void*)vertices);
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, (void*)indices);
glDisableClientState(GL_VERTEX_ARRAY);
glEnable(GL_CULL_FACE);
关于c++ - 曲面 segmentation 的理论和算法，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/33124211/