void DrawGLScene() // Main Drawing Routine
{
GLmatrix16f Minv, Inv;
GLvector4f lp;
// Clear Color Buffer, Depth Buffer, Stencil Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glColor4f(0.7f, 0.4f, 0.0f, 1.0f);
glLoadIdentity();
glPushMatrix(); {
glTranslatef(0.0f, 0.0f, -20.0f); // Zoom Into Screen 20 Units
glLightfv(GL_LIGHT1, GL_POSITION, LightPos); // Position Light1
glTranslatef(SpherePos[0], SpherePos[1], SpherePos[2]); // Position The Sphere
gluSphere(q, 1.5f, 32, 16); // Draw A Sphere
} glPopMatrix();
glPushMatrix(); {
glTranslatef(0.0f, 0.0f, -20.0f); // Zoom Into The Screen 20 Units
DrawGLRoom(); // Draw The Room
glTranslatef(ObjPos[0], ObjPos[1], ObjPos[2]); // Position The Object
glRotatef(xrot, 1.0f, 0.0f, 0.0f); // Spin It On The X Axis By xrot
glRotatef(yrot, 0.0f, 1.0f, 0.0f); // Spin It On The Y Axis By yrot
DrawGLObject(obj); // Procedure For Drawing The Loaded Object
// 获得光源的位置(返回值是在视觉坐标系下的)
glGetLightfv(GL_LIGHT1, GL_POSITION, lp);
glGetFloatv(GL_MODELVIEW_MATRIX, Minv);
m3dInvertMatrix44(Inv, Minv);
// 把光源位置从视觉坐标系下变换到当前的场景坐标系(obj)下.
VMatMult(Inv, lp);
// 开始渲染阴影
CastShadow(&obj, lp);
// 用一个小黄球标记出光源的位置
glPushMatrix(); {
glColor4f(0.7f, 0.4f, 0.0f, 1.0f); // Set Color To Purplish Blue
glDisable(GL_LIGHTING); // Disable Lighting
glDepthMask(GL_FALSE); // Disable Depth Mask
glTranslatef(lp[0], lp[1], lp[2]);
gluSphere(q, 0.2f, 16, 8);
glEnable(GL_LIGHTING); // Enable Lighting
glDepthMask(GL_TRUE); // Enable Depth Mask
} glPopMatrix();
} glPopMatrix();
xrot += xspeed;
yrot += yspeed;
glFlush();
glutSwapBuffers();
}
void SceneTutorial27::Draw()
{
Scene::Draw();
float Minv[16];
float wlp[4];
float lp[4];
// Clear Color Buffer, Depth Buffer, Stencil Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glLoadIdentity(); // Reset Modelview Matrix
glTranslatef(0.0f, 0.0f, -20.0f); // Zoom Into Screen 20 Units
glLightfv(GL_LIGHT1, GL_POSITION, LightPos); // Position Light1
glTranslatef(SpherePos[0], SpherePos[1], SpherePos[2]); // Position The Sphere
gluSphere(q, 1.5f, 32, 16); // Draw A Sphere
// calculate light's position relative to local coordinate system
// dunno if this is the best way to do it, but it actually works
// if u find another aproach, let me know ;)
// we build the inversed matrix by doing all the actions in reverse order
// and with reverse parameters (notice -xrot, -yrot, -ObjPos[], etc.)
glLoadIdentity(); // Reset Matrix
glRotatef(-yrot, 0.0f, 1.0f, 0.0f); // Rotate By -yrot On Y Axis
glRotatef(-xrot, 1.0f, 0.0f, 0.0f); // Rotate By -xrot On X Axis
glGetFloatv(GL_MODELVIEW_MATRIX,Minv); // Retrieve ModelView Matrix (Stores In Minv)
lp[0] = LightPos[0]; // Store Light Position X In lp[0]
lp[1] = LightPos[1]; // Store Light Position Y In lp[1]
lp[2] = LightPos[2]; // Store Light Position Z In lp[2]
lp[3] = LightPos[3]; // Store Light Direction In lp[3]
VMatMult(Minv, lp); // We Store Rotated Light Vector In 'lp' Array
glTranslatef(-ObjPos[0], -ObjPos[1], -ObjPos[2]); // Move Negative On All Axis Based On ObjPos[] Values (X, Y, Z)
glGetFloatv(GL_MODELVIEW_MATRIX,Minv); // Retrieve ModelView Matrix From Minv
wlp[0] = 0.0f; // World Local Coord X To 0
wlp[1] = 0.0f; // World Local Coord Y To 0
wlp[2] = 0.0f; // World Local Coord Z To 0
wlp[3] = 1.0f;
VMatMult(Minv, wlp); // We Store The Position Of The World Origin Relative To The
// Local Coord. System In 'wlp' Array
lp[0] += wlp[0]; // Adding These Two Gives Us The
lp[1] += wlp[1]; // Position Of The Light Relative To
lp[2] += wlp[2]; // The Local Coordinate System
glColor4f(0.7f, 0.4f, 0.0f, 1.0f); // Set Color To An Orange
glLoadIdentity(); // Reset Modelview Matrix
glTranslatef(0.0f, 0.0f, -20.0f); // Zoom Into The Screen 20 Units
DrawGLRoom(); // Draw The Room
glTranslatef(ObjPos[0], ObjPos[1], ObjPos[2]); // Position The Object
glRotatef(xrot, 1.0f, 0.0f, 0.0f); // Spin It On The X Axis By xrot
glRotatef(yrot, 0.0f, 1.0f, 0.0f); // Spin It On The Y Axis By yrot
DrawShadowedObject(obj); // Procedure For Drawing The Loaded Object
castShadow(obj, lp ); // Procedure For Casting The Shadow Based On The Silhouette
glColor4f(0.7f, 0.4f, 0.0f, 1.0f); // Set Color To Purplish Blue
glDisable(GL_LIGHTING); // Disable Lighting
glDepthMask(GL_FALSE); // Disable Depth Mask
glTranslatef(lp[0], lp[1], lp[2]); // Translate To Light's Position
// Notice We're Still In Local Coordinate System
gluSphere(q, 0.2f, 16, 8); // Draw A Little Yellow Sphere (Represents Light)
glEnable(GL_LIGHTING); // Enable Lighting
glDepthMask(GL_TRUE); // Enable Depth Mask
glutSwapBuffers();
}
