OpenGL - change light of a 3D sphere with popup menu - c++

I had updated after the suggestion in the comment sections. It should be better and working fine now. However, feel free to comment and discussion! I really wish to improve my programming in OpenGL!
I am new to OpenGL. I want to create a pop-up menu to change the lighting (ambient, diffuse, specular and position) of a sphere. However, there are some problems in showing the light. It works accordingly to click on the choice, e.g. ambient--> diffuse --> specular) but cannot work when (specular--> diffuse).
Here is the part of my code.
void display(void)
{
GLfloat gray[] = { 0.8, 0.8, 0.8, 1.0 };
GLfloat cyan[] = { 0.0, 1.0, 1.0, 0.0 };
GLfloat black[] = { 0.0, 0.0, 0.0, 1.0 };
GLfloat white[] = { 0.8f, 0.8f, 0.8f, 1.0f };
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glTranslatef(0.0, 0.0, tdist);
glRotatef((GLfloat)spinx, 1.0, 0.0, 0.0);
glRotatef((GLfloat)spiny, 0.0, 1.0, 0.0);
glRotatef((GLfloat)spinz, 0.0, 0.0, 1.0);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, gray);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, cyan);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, white);
glMaterialfv(GL_FRONT_AND_BACK, GL_POSITION, cyan);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 50);
glEnable(GL_LIGHTING);
glEnable(GL_POLYGON_OFFSET_FILL);
if (value == 2) {
glEnable(GL_LIGHT0);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
}
else if (value == 3) {
glEnable(GL_LIGHT1);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
}
else if (value == 4) {
glEnable(GL_LIGHT2);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
}
else if (value == 5) {
glEnable(GL_LIGHT3);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
}
glDisable(GL_POLYGON_OFFSET_FILL);
glDisable(GL_LIGHTING);
glDisable(GL_LIGHT0);
glDisable(GL_LIGHT1);
glDisable(GL_LIGHT2);
glDisable(GL_LIGHT3);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glCallList(list);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glPopMatrix();
glFlush();
}
Thank you so much if anyone can help!!!

Related

OPENGL lighting result comes out wrong

my desired outcome(in red)
Hi, I'm trying to make my code in opengl c++ to produce this(with light coming from (1,1,1)), and it doesn't work and produces this. Can anyone teach me why?
I thought it was about matrices calculation or lighting usage at first, but not so sure anymore.
light function
void init_light(void) {
glLoadIdentity();
glGetFloatv(GL_PROJECTION_MATRIX, ProjectionMat);
ProjectionMatrix = glm::make_mat4(ProjectionMat);
glGetFloatv(GL_MODELVIEW_MATRIX, ViewMat);
ViewMatrix = glm::make_mat4(ViewMat);
glm::mat4 InverseProjectionMatrix = glm::inverse(ProjectionMatrix);
glm::mat4 InverseViewMatrix = glm::inverse(ViewMatrix);
glm::mat4 M = glm::inverse(ProjectionMatrix * ViewMatrix);
glm::mat4 Matr = ProjectionMatrix * ViewMatrix;
glClearColor(1.0, 1.0, 1.0, 0.0);
//glClearDepth(0.0);
GLfloat ambient[] = { 0.2, 0.2, 0.2, 1.0 };
GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat specular[] = { 1.0, 1.0, 1.0, 1.0 };
//GLfloat position0[] = { 1., 1., 1., 0.0 };
//GLfloat position1[] = { 1., 1., 1., 1.0 };
GLfloat pos[] = { (GLfloat)(InverseViewMatrix * glm::make_vec4(position0))[0],
(GLfloat)(InverseViewMatrix * glm::make_vec4(position0))[1],
(GLfloat)(InverseViewMatrix * glm::make_vec4(position0))[2],
(GLfloat)(InverseViewMatrix * glm::make_vec4(position0))[3] };
GLfloat spot_direction[] = { 1.0, 1.0, 1.0 };
glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction);
glLightf(GL_LIGHT1, GL_SPOT_CUTOFF, 1.0);
glLightf(GL_LIGHT1, GL_SPOT_EXPONENT, 80.);
//glLightfv(GL_LIGHT0, GL_POSITION, position0);
//glLightfv(GL_LIGHT0, GL_POSITION, pos);
//glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, 2.0);
//glLightfv(GL_LIGHT1, GL_AMBIENT, ambient);
//glLightfv(GL_LIGHT1, GL_DIFFUSE, diffuse);
//glLightfv(GL_LIGHT1, GL_POSITION, position1);
GLfloat mat_ambient[] = { 0.2, 0.2, 0.8, 0.0 };
GLfloat mat_diffuse[] = { 1.0, 1.0, 1.0, 0.0 };
GLfloat mat_specular[] = { 0.5, 0.5, 0.5, 0.0 };
//GLfloat mat_emissive[] = { 0.0, 0.0, 0.0, 0.0 };
GLfloat mat_shininess[] = { 120.0 };
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
//glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, mat_emissive);
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
glColorMaterial(GL_FRONT, GL_SHININESS);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHT1);
glEnable(GL_NORMALIZE);
glEnable(GL_AUTO_NORMAL);
glShadeModel(GL_SMOOTH);
glEnable(GL_DEPTH_TEST);
}
rendering scene
void renderScene(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
double ratio = window_size[0] * 1.0 / window_size[1];
if (rotationbool == 1) {
xRot = temp_xRot;
yRot = temp_yRot;
}
glPopMatrix();
gluPerspective(fovy, ratio, zNear + (zoom_factor)* ratio, zFar + (zoom_factor)* ratio);
glLightfv(GL_LIGHT0, GL_POSITION, position0);
glLightfv(GL_LIGHT1, GL_POSITION, position1);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glPopMatrix();
glRotatef(xRot, 1.0, .0, .0);
glRotatef(yRot, .0, 1.0, .0);
glTranslatef(xTrans, yTrans, zTrans);
glPushMatrix(); ...
}
main function
int main(int argc, char* argv[]) {
bool cad_draw = true;
if (cad_draw) {
glutInit(&argc, argv);
}
double L_base[3] = { 0.1, 0.1, 0.1 };
if (cad_draw) {
finemost_limit[0] = L_base[0];
finemost_limit[1] = L_base[1];
finemost_limit[2] = L_base[2];
window_params_init();
//glDepthRange(1.0, 0.);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glEnable(GL_DEPTH_TEST);
glDepthMask(GL_FALSE);
glutInitWindowPosition(100, 100);
glutInitWindowSize(window_size[0], window_size[1]);
glutCreateWindow("Interactive boundary design");
glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_CONTINUE_EXECUTION);
//init_sfc();
//init_light();
// register callbacks
glDepthFunc(GL_LEQUAL);
//glDepthFunc(GL_GEQUAL);
glDepthRange(1.0, 0.); // left handed에서 right hanaded로 변경
glutDisplayFunc(renderScene);
glutReshapeFunc(changeSize);
init_light();
///glutMouseWheelFunc(render_wheel);
glutMouseFunc(mousePress);
glutMotionFunc(mouseDrag);
glutPassiveMotionFunc(passive_mouse);
glutKeyboardFunc(simple_keyboard_binding);
// enter GLUT event processing cycle
glutMainLoop();
}
return 0;
}

Not all objects with same material look the same - Open GL/C++

So I have drawn 5 tori on my scene and a cube behind them and besides LIGHT0 I also have LIGHT1 enabled on click. I need to create two different materials where when I press on number 1 material 1 turns on, and when I press 2 material two turns on instead of material one. But what happens is, those materials get turned on only for tori, not the cube behind them. Here is everything in the code explained:
void light_1() {
GLfloat light_position[] = {1.0f, 1.0f, 1.0f, 0.0f};
GLfloat light_specular[] = {1.0f, 1.0f, 1.0f, 5.0f};
glLightfv(GL_LIGHT1, GL_POSITION, light_position);
glLightfv(GL_LIGHT1, GL_SPECULAR, light_specular);
}
Cube and tori have same exact properties.
void drawCube() {
GLfloat mat_diffuse[] = {0.3, 0.0, 0.7, 1.0};
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat_diffuse);
glutSolidCube(7.5);
}
void greenTorus() {
GLfloat mat_diffuse[] = {0.0, 1.0, 0.0, 1.0};
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat_diffuse);
glutSolidTorus(0.08, 0.8, 30, 30);
}
Here is my display function. Ignore the variables, they are controled by different stuff and are irrelevant.
void display(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(75.0, 4.0/3.0, 1.0, 200.0);
light_1();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0+LR, 0.0+UD, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
glPushMatrix();
glTranslatef(0.0+tyg/2, 0.0-tbr/2, -5.0);
glRotated(a, 0, 0, 1);
glScaled(0.5+s, 0.5+s, 0.5+s);
greenTorus();
glPopMatrix();
glPushMatrix();
glTranslatef(0.0, -0.5, -9.0);
drawCube();
glPopMatrix();
glFlush();
glutPostRedisplay();
}
Here is the material that is used for bottom image.
void material_1() {
GLfloat m_ambient[] = {0.33f, 0.23f, 0.03f, 1.0f};
GLfloat m_diffuse[] = {0.8f, 0.6f, 0.1f, 1.0f};
GLfloat m_specular[] = {2.0f, 2.0f, 2.0f, 1.0f};
GLfloat m_shininess = 128.0f;
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, m_ambient);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, m_diffuse);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, m_specular);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, m_shininess);
}
Does anyone see the issue? Here is a screenshot of the scene whole program renders when lights 0 and 1 are both turned on and material_1 is turned on. Why isn't the cube also highlighted? Why does LIGHT0 light on all objects, but LIGHT1 only on tori?

OpenGL Lighitng

I am new to OpenGL, I made this to switch menu in between ambient, diffuse and specular, position light. It works but looks weird
The code (relevant part ) is:
void gfxinit(void)
{
GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 };
GLfloat light_diffuse[] = { 1.0, 0.0, 1.0, 1.0 };
GLfloat light_direction[] = { -1, -2, -1, 1 };
GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat light_position[] = { 0.0, 0.0, 1.0, 0.0 };
GLfloat global_ambient[] = { 0.2, 0.2, 0.2, 1.0 };
glClearColor(0.0, 0.0, 0.0, 1.0); //background Color
list = glGenLists(1);
glNewList(list, GL_COMPILE);
glutSolidSphere(1.0, 30, 12);
glEndList();
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, global_ambient);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT1, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT2, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT3, GL_POSITION, light_position);
glLightf(GL_LIGHT4, GL_SPOT_EXPONENT, 2.0);
}
and
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glTranslatef(0.0, 0.0, tdist);
glRotatef((GLfloat)spinx, 1.0, 0.0, 0.0);
glRotatef((GLfloat)spiny, 0.0, 1.0, 0.0);
glRotatef((GLfloat)spinz, 0.0, 0.0, 1.0);
glMaterialfv(GL_FRONT, GL_AMBIENT, gray);
glMaterialfv(GL_FRONT, GL_DIFFUSE, cyan);
glMaterialfv(GL_FRONT, GL_SPECULAR, gray);
glMaterialfv(GL_FRONT, GL_POSITION, white);
glMaterialf(GL_FRONT, GL_SHININESS, 70);
glMaterialfv(GL_FRONT, GL_SPECULAR, light_param);
glEnable(GL_LIGHTING);
glEnable(GL_POLYGON_OFFSET_FILL);
if (value == 2) {//ambient
glEnable(GL_LIGHT0);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
glDisable(GL_LIGHT0);
}
else if (value == 3) {//diffuse
glEnable(GL_LIGHT1);
glPolygonOffset(polyfactor, polyunits);
glCallList(list);
glDisable(GL_LIGHT1);
}
Really thanks if someone can tell me whether there is mistake here or not! Thanks!

How to fix bitmap lighting in openGL?

I need help with my code in C++ using the OpenGL API. I have written a program that draws 4 3D cubes and text (using bitmap) onto the screen. Now I want to add lighting.
I have added glMaterial code to give a description of the material for the cubes. I do not want the material properties to be applied to the bitmap text. Therefore, I placed the code for the material before drawing the cube and I also placed the code for drawing the cube and the material between a pushMatrix and popMatrix pair. However, when I run the code, I find the text changes color.
Below is some of the code that I am using:
void init() {
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ligAmb);
glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lig[0][0]);
glLightfv(GL_LIGHT0, GL_SPECULAR, lig[0][1]);
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, ligDir);
glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, exp_one);
glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, cutoff);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT1, GL_DIFFUSE, lig[1][0]);
glLightfv(GL_LIGHT1, GL_SPECULAR, lig[1][1]);
glEnable(GL_LIGHT1);
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}
void drawCube(Point3D colors[], Point3D vertices[]) {
glBegin(GL_QUADS);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[0]);
glVertex3fv(vertices[0]);
glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);
glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[0]);
glVertex3fv(vertices[0]);
glColor3fv(colors[0]);
glVertex3fv(vertices[0]);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glEnd();
}
void displayObject() {
glPushMatrix();
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLightfv(GL_LIGHT0, GL_POSITION, ligPos[0]);
glLightfv(GL_LIGHT1, GL_POSITION, ligPos[1]);
typedef GLint vertex3[3];
Point3D vertices[8] = { {-1.0, -1.0, -1.0},
{-1.0, -1.0, 1.0},
{-1.0, 1.0, -1.0},
{-1.0, 1.0, 1.0},
{ 1.0, -1.0, -1.0},
{ 1.0, -1.0, 1.0},
{ 1.0, 1.0, -1.0},
{ 1.0, 1.0, 1.0} };
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_INT, 0, vertices);
GLubyte vertIndex[] = { 6,2,3,7,5,1,0,4,7,3,1,5,4,0,2,6,2,0,1,3,7,5,4,6
};
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_BYTE, vertIndex);
glPopMatrix();
Point3D colorsb[8] = { {0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.},
{0.,0.,1.} };
Point3D colorsg[8] = { {0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.},
{0.,1.,0.} };
Point3D colorsr[8] = { {1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.},
{1.,0.,0.} };
Point3D colorsy[8] = { {1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.},
{1.,1.,0.} };
glPushMatrix();
glTranslatef(-0.5f, 4.0f, -6.0f);
glRotatef(10.0, 0.0, 1.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[0][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[0][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[0][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[0]);
drawCube(colorsb, vertices);
glPopMatrix();
glPushMatrix();
glTranslatef(6.0f, -0.5f, -6.0f);
glRotatef(10.0, 1.0, 0.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[1][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[1][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[1][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[1]);
drawCube(colorsg, vertices);
glPopMatrix();
glPushMatrix();
glTranslatef(-0.5f, -4.5f, -6.0f);
glRotatef(10.0, 0.0, 1.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[2][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[2][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[2][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[2]);
drawCube(colorsr, vertices);
glPopMatrix();
glPushMatrix();
glTranslatef(-6.0f, -0.5f, -6.0f);
glRotatef(10.0, 1.0, 0.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[3][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[3][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[3][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[3]);
drawCube(colorsy, vertices);
glPopMatrix();
}
void display() {
displayObject();
wordColor = "green";
char str[] = { "Red" };
glColor3f(0.0, 1.0, 0.0);
glRasterPos2f(-0.5, 0.0);
for (int i = 0; i < strlen(str); i++)
{
glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, str[i]);
}
glPopMatrix();
loop += 0.05;
glFlush();
glutSwapBuffers();
glutPostRedisplay();
}
OpenGL is a state machine, which means that it keeps a state around until you explicitly change it again. So when you take care to set the illumination only after drawing the text during drawing one frame, it will have happened before drawing the text of the next frame.
The solution is, that you always set every relevant state for whatever it is you're drawing, right before you draw it. In case of the text, it's as simple as disable lighting, right before drawing the text (actually before calling glRasterPos).

How to use spot light in opengl

I am trying to learn how to use a spot light in OpenGL. I wish to shine a spot (torch) light from a point marked (lighpos), and shown as grey dot, onto the side of a GLUT teapot centered at (possph) in 3D space. I have attached an example where I have tried to do this but I cannot get the light to focus on the teapot. I am expecting a almost touch light focus based on the parameters I have tried to use.
Could someone point out what I have missed / mistake I have made.
Thanks
Stuart
#include <windows.h>
#include <GL/glut.h>
#include <stdio.h>
GLfloat lighpos[] = { -300., 200., 250., 1.0 }; // Location of light
GLfloat possph[] = { -50., 350., 150. }; // Position of teapot
GLfloat ligdir[] = { 250., 150., -100. }; // Direction from light to teapot
void init(void) {
glClearColor(0.0, 0.0, 0.0, 0.0);
glShadeModel(GL_SMOOTH);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_DEPTH_TEST);
glLightfv(GL_LIGHT0, GL_POSITION, lighpos);
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, ligdir);
glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 10.0);
GLfloat ambientLight0[] = { 0.25, 0.25, 0.25, 1.0 };
glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight0);
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientLight0);
GLfloat diffuseLight0[] = { 1.0, 1.0, 1.0, 1.0 };
glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight0);
GLfloat specularLight0[] = { 1.0, 1.0, 1.0, 1.0 };
glLightfv(GL_LIGHT0, GL_SPECULAR, specularLight0);
glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, 128.0f);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
void drawAxis() {
glBegin(GL_LINES);
glColor3f(1.0, 0.0, 0.0); glVertex3f(-500., 0.0, 0.0); glVertex3f(500., 0.0, 0.0);
glColor3f(0.0, 1.0, 0.0); glVertex3f(0.0, -500., 0.0); glVertex3f(0.0, 500., 0.0);
glColor3f(0.0, 0.0, 1.0); glVertex3f(0.0, 0.0, -500.); glVertex3f(0.0, 0.0, 500.);
glEnd();
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
drawAxis();
glPushMatrix();
glPointSize(10);
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_POINTS);
glVertex3d(lighpos[0], lighpos[1], lighpos[2]);
glEnd();
glPopMatrix();
glColor3f(1., 0., 0.);
glPushMatrix();
glTranslated(possph[0], possph[1], possph[2]);
glutSolidTeapot(100.);
glPopMatrix();
glutSwapBuffers();
}
void reshape(int w, int h) {
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-1.0, 1.0, -1.0, 1.0, 4, 3000.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(1500.0, 1500.0, 1500.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowPosition(0.0, 0.0);
glutInitWindowSize(800, 800);
glutCreateWindow("spotlight");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
Fixed function pipeline illumination, which is what you are using in your code, performs lighting calculations only at the vertices. If your spotlight illuminates only a few or a single vertex you'll not get a pleasing spotlight effect. One possible solution would be to highly refine your models' meshes. The better, much more efficient and elegant solution is to drop using the fixed function pipeline and implement a illumination fragment shader, so that lighting is calculated for each pixel.