The following code is a calculation of a fish that is drawn by OpenGL, I would like someone to explain to me please.
GoldfishGeometry::GoldfishGeometry() :
m_BodySegments(50),
m_CircleSegments(25),
m_StripSegments(50)
{
m_InnerCurve.p0 = Vec2f(0.0f, 0.0f);
m_InnerCurve.p1 = Vec2f(0.8f, 0.1f);
m_InnerCurve.p2 = Vec2f(0.2f, 0.9f);
m_InnerCurve.p3 = Vec2f(0.0f, 1.0f);
m_OuterCurve.p0 = Vec2f(0.0f, 0.0f);
m_OuterCurve.p1 = Vec2f(0.8f, 0.1f);
m_OuterCurve.p2 = Vec2f(1.0f, 0.5f);
m_OuterCurve.p3 = Vec2f(1.0f, 1.0f);
m_EndCurve.p0 = Vec2f(0.0f, 0.0f);
m_EndCurve.p1 = Vec2f(5.0f, 0.1f);
m_EndCurve.p2 = Vec2f(5.0f, 0.5f);
m_EndCurve.p3 = Vec2f(0.0f, 1.0f);
std::vector< float > cylVerts;
cylVerts.reserve(((int)m_CircleSegments+1)*3*2*(int)m_BodySegments);
std::vector< float > cylNormals;
cylNormals.reserve(((int)m_CircleSegments+1)*3*2*(int)m_BodySegments);
std::vector< float > cylTexcoords;
cylTexcoords.reserve(((int)m_CircleSegments+1)*2*2*(int)m_BodySegments);
float x, y0, y1, z, u, v, angle;
float hStep = 1.0f / m_BodySegments;
float angleStep = ( 360.0f/(float)(m_CircleSegments) ) * 3.14159265f / 180.0f;
float texcoordStep = 1.0f/(float)(m_CircleSegments);
unsigned int hOffsetVerts = ((int)m_CircleSegments + 1)*3;
unsigned int hOffsetTex = ((int)m_CircleSegments + 1)*2;
for ( unsigned int h=0; h<(int)m_BodySegments; ++h )
{
for (unsigned int c=0; c<=(int)m_CircleSegments; ++c )
{
unsigned int offsetVerts = c*3;
unsigned int offsetTex = c*2;
angle = c*angleStep;
x = sin(angle);
z = cos(angle);
y0 = h*hStep; y1 = (h+1)*hStep;
u = c*texcoordStep;
cylVerts.push_back(x);
cylVerts.push_back(y0);
cylVerts.push_back(z);
cylNormals.push_back(x);
cylNormals.push_back(0.0f);
cylNormals.push_back(z);
cylTexcoords.push_back(u);
cylTexcoords.push_back(y0);
cylVerts.push_back(x);
cylVerts.push_back(y1);
cylVerts.push_back(z);
cylNormals.push_back(x);
cylNormals.push_back(0.0f);
cylNormals.push_back(z);
cylTexcoords.push_back(u);
cylTexcoords.push_back(y1);
}
}
std::vector< float > stripVerts;
std::vector< float > stripNormals;
std::vector< float > stripTexcoords;
stripVerts.reserve(((int)m_StripSegments)*3*2*(int)m_BodySegments);
stripNormals.reserve(((int)m_StripSegments)*3*2*(int)m_BodySegments);
stripTexcoords.reserve(((int)m_StripSegments)*2*2*(int)m_BodySegments);
float stripStep = 1.0f/(float)(m_StripSegments);
for ( unsigned int h=0; h<(int)m_BodySegments; ++h )
{
for (unsigned int v=0; v<(int)m_StripSegments; ++v )
{
u = v * stripStep;
y0 = h*hStep; y1 = (h+1)*hStep;
x = v * stripStep;
stripVerts.push_back(x);
stripVerts.push_back(y0);
stripVerts.push_back(0.0f);
stripNormals.push_back(0.0f);
stripNormals.push_back(0.0f);
stripNormals.push_back(1.0f);
stripTexcoords.push_back(u);
stripTexcoords.push_back(y0);
stripVerts.push_back(x);
stripVerts.push_back(y1);
stripVerts.push_back(0.0f);
stripNormals.push_back(0.0f);
stripNormals.push_back(0.0f);
stripNormals.push_back(1.0f);
stripTexcoords.push_back(u);
stripTexcoords.push_back(y1);
}
}
glGenVertexArrays(2, &m_VAO[0]);
glGenBuffers(6, &m_VBO[0]);
glBindVertexArray(m_VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[0]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_CircleSegments+1)*3*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&cylVerts[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)0);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[1]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_CircleSegments+1)*2*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&cylTexcoords[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)1, 2, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)1);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[2]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_CircleSegments+1)*3*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&cylNormals[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)2, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)2);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glBindVertexArray(m_VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[3]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_StripSegments)*3*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&stripVerts[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)0);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[4]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_StripSegments)*2*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&stripTexcoords[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)1, 2, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)1);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO[5]);
glBufferData(GL_ARRAY_BUFFER, ((int)m_StripSegments)*3*2*((int)m_BodySegments)*sizeof(float), (const GLvoid *)&stripNormals[0], GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)2, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray((GLuint)2);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
[/quote]
}
explaining a piece of code
It looks like this code is supposed to create a fish from some geometry (by starting with a few default lines and "shaping" the fish by pushing vertices back and forth to approximate a goldfish's outline, using a sinuosidal pattern), and then displays it via OpenGL (apparently just using solid lines). In immediate mode.
Talk about reusability...
Talk about reusability...
This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement