I want to add a Light source to my OpenGl code.
I have added following code to my init function...
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glLightf(GL_LIGHT0, GL_POSITION,(50.0,0.0,0.0,1.0));
Moreover I have drawn a quad:
glBegin(GL_QUADS);
glNormal3f(0.0,0.0,1.0);
glVertex3f(0.0,0.0,20.0);
glVertex3f(0.0,10.0,20.0);
glVertex3f(10.0,10.0,20.0);
glVertex3f(10.0,0.0,20.0);
glEnd();
But no matter what value I use for the Position,
the lighting doesn't change at all...
glLightf(GL_LIGHT0, GL_POSITION,(50.0,0.0,0.0,1.0));
^^^^^^^^^^^^^^^^^^
(50.0,0.0,0.0,1.0) in this context will evaluate to the last expression in the list (1.0). Probably not what you want.
You need to use a real array and glLightfv() to specify light positions:
GLfloat pos[] = { 50.0, 0.0, 0.0, 1.0 };
glLightfv( GL_LIGHT0, GL_POSITION, pos );
Related
I am building a house in OpenGL. On the outside and on the inside where there are doors or windows, I use a Quad to go below and above the windows all the way around the house, and then a quad to fill in the gaps between windows. These will have the same plane value, but for some reason GL_LIGHT passes shadows onto some. Any clue why?
Quad between windows
glBegin(GL_QUADS);
glTexCoord2d(0, 0);glVertex3d(0, 1.1, 0);
glTexCoord2d(2, 0);glVertex3d(0, 1.1, 2);
glTexCoord2d(2, 1.6);glVertex3d(0, 2.7, 2);
glTexCoord2d(0, 1.6);glVertex3d(0, 2.7, 0);
glEnd();
Below windows
glBegin(GL_QUADS);
glTexCoord2d(0, 0);glVertex3d(0, 0.1, 0);
glTexCoord2d(15, 0);glVertex3d(0, 0.1, 15);
glTexCoord2d(15, 1);glVertex3d(0, 1.1, 15);
glTexCoord2d(0.0, 1);glVertex3d(0, 1.1, 0);
glEnd();
Above windows
glBegin(GL_QUADS);
glTexCoord2d(0, 2.6);glVertex3d(0, 2.7, 0);
glTexCoord2d(15, 2.6);glVertex3d(0, 2.7, 15);
glTexCoord2d(15, 3.0);glVertex3d(0, 3.1, 15);
glTexCoord2d(0.0,3.0);glVertex3d(0, 3.1, 0);
glEnd();
here is the code for the light
GLfloat light_position[] = { 50, 50, -1.0};
GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat ambient[] = { 1.0, 1.0, 1.0, 1.0 };
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHT1);
glEnable(GL_NORMALIZE);
glLightfv(GL_LIGHT0, GL_POSITION , light_position );
glLightfv(GL_LIGHT0, GL_SPECULAR , specular);
glLightfv(GL_LIGHT0, GL_DIFFUSE , diffuse );
glLightfv(GL_LIGHT0, GL_AMBIENT , ambient );
Here is a screenshot of the result
http://imgur.com/WsgZWBF
Why is it doing this, and is there any way to fix it?
You need to supply (meaningful) vertex/face normals for OpenGL's lighting to work properly:
18.020 Why are my objects all one flat color and not shaded and illuminated?
This effect occurs when you fail to supply a normal at each vertex.
OpenGL needs normals to calculate lighting equations, and it won't calculate normals for you (with the exception of evaluators). If your application doesn't call glNormal*(), then it uses the default normal of (0.0, 0.0, 1.0) at every vertex. OpenGL will then compute the same, or nearly the same, lighting result at each vertex. This will cause your model to look flat and lack shading.
The solution is to simply calculate the normals that need to be specified at any given vertex. Then send them to OpenGL with a call to glNormal3f() just prior to specifying the vertex, which the normal is associated with.
I'm trying to render an object (say cube) with OpenGL 1.1 (I know that doesn't makes sense nowadays, but I've to use this). Everything works fine until I try some lighting.
Here's the problem:
The Global variable set are:
static GLfloat light_position[] = {1.0, 1.0, 2*cZ.x , 0.0};
// cZ.x is the minimum z of the mesh. I know
// this is at infinity, but don't work also with w=1.0
In the main function:
...
glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix
glLoadIdentity(); // Reset The Modelview Matrix
glEnable(GL_LIGHT0);
glEnable(GL_LIGHTING);
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
....
Drawing a mesh k
// While drawing mesh k
GLfloat light_ambient[] = {COLOUR[k][0], COLOUR[k][1], COLOUR[k][2], 1.0};
GLfloat light_diffuse[] = {COLOUR[k][0], COLOUR[k][1], COLOUR[k][2], 1.0};
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
....
//This is a mesh, so will be drawn using triangles
glBegin(GL_TRIANGLES);
//Triangles will be defined by vertex indices in faces
for (unsigned int i = 0; i<mesh->faces.size(); i++){
int index1 = mesh->faces.at(i).x;
int index2 = mesh->faces.at(i).y;
int index3 = mesh->faces.at(i).z;
glNormal3f(mesh->normals.at(i).x,mesh->normals.at(i).y,mesh->normals.at(i).z);
glVertex3f(mesh->vertices.at(index1).x, mesh->vertices.at(index1).y, mesh->vertices.at(index1).z);
glVertex3f(mesh->vertices.at(index2).x, mesh->vertices.at(index2).y, mesh->vertices.at(index2).z);
glVertex3f(mesh->vertices.at(index3).x, mesh->vertices.at(index3).y, mesh->vertices.at(index3).z);
}
glEnd();
....
Whereas the normal are computed as:
glm::vec3 currFace = m->faces.at(faceIndex);
glm::vec3 vert1 = m->vertices.at(currFace.x);
glm::vec3 vert2 = m->vertices.at(currFace.y);
glm::vec3 vert3 = m->vertices.at(currFace.z);
glm::vec3 side1 = (vert2 - vert1);
glm::vec3 side2 = (vert3 - vert1);
glm::vec3 normal = glm::cross(side1, side2);
normal = glm::normalize(normal);
I'm really struggling to understand what's wrong, can you point me in the right direction?
EDIT: This happens similarly with the standford bunny (taken from standford repo, so it's well formed)
http://imgur.com/Z6225QG
Looking at your normals picture it looks like that more than not being shaded, some of your object faces are transparent.
I used to have a similar problem while learning OpenGL, in my case I forgot to enable DEPTH_TEST. You can do it simply adding this line to your GL init function function:
glEnable(GL_DEPTH_TEST);
Give it a try
anyone can teach me how to draw 2 objects, for example a cube and a sphere, in origin (0, 0, 0) and when i move the cube, the sphere just remains in the origin. same with moving the sphere, the cube remains..
using keyboardfunc.
if (!LightSwitch)
{
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glPushMatrix();
glTranslatef(CubeX, CubeY, CubeZ);
glColor3f(1.0, 0.0, 0.0);
glPushAttrib(GL_LIGHTING_BIT | GL_CURRENT_BIT);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, Green);
glutSolidCube(2.0);
glPopAttrib();
glPopMatrix();
glEnd();
}
if (!LightSwitch1)
{
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT1);
glPushMatrix();
glTranslatef(AxisX, AxisY, AxisZ);
glColor3f(1.0, 0.0, 0.0);
glPushAttrib(GL_LIGHTING_BIT | GL_CURRENT_BIT);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, Blue);
glutSolidSphere(2.0, 10.0, 5.0);
glPopAttrib();
glPopMatrix();
}
glEnd();
I'm no expert, but I believe that by having separate glPushMatrix() / glPopMatrix() blocks for the sphere and the cube, you are giving each object its own local coordinate system. This is why they transform independent of each other.
If you want to move them together, you need to specify glTranslate() outside your glPushMatrix() / glPopMatrix() first:
glTranslatef(translation....); // Translates the whole scene
glPushMatrix();
glTranslatef(the sphere); // Sphere & cube locations changeable via keyb.
glTranslatef(the cube);
glPopMatrix();
If you want to, say, rotate the cube with respect to the sphere (ie., make the center of the sphere the origin of the cube's coordinate system), make a new glPushMatrix()/glPopMatrix() block nested within the first block:
glPushMatrix();
glTranslatef(the sphere);
glPushMatrix();
glRotatef(the cube); // Rotate about specific axis of the sphere
glPopMatrix();
glPopMatrix();
I believe your code is correct for drawing the sphere at location Axis and the cube at location Cube. You say you are using a keyboard func and it is moving them both together when you want to move just one. I believe you are updating both sets of variables in your keyboard function. Try printing out CubeXYZ and AxisXYZ and make sure you're getting the right thing.
i want to draw a rotating cube in the middle of the screen, and i want it to be lit by a light above it (i want it to look as if the cube was being lit from a fixed screen position). my problem is that i don't know how to prevent the light from rotating with the cube.
here's the code:
(SUMMARY: initGL, paintGL, and resizeGl are the functions that you always have to implement. in paintGL i use makeCube(). in makeCube() i use glBegin(GL_QUADS) to make a cube,and i use calcNormals() to calculate the normals of the cube )
-------------initGL--------------------------
angle=0.0;
glEnable (GL_DEPTH_TEST);
glEnable (GL_LIGHTING);
GLfloat LightDiffuse[]= { 1.0f, 1.0f, 1.0f, 1.0f };
GLfloat LightPosition[]= { 0.0f, 1.5f,1.5f, 1.0f };
glLightfv(GL_LIGHT0, GL_DIFFUSE, LightDiffuse);
glLightfv(GL_LIGHT0, GL_POSITION,LightPosition);
glEnable (GL_LIGHT0);
--------------paintGL------------------
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -13.0);
glRotatef(angle,0.0f,1.0f,0.0f);
makeCube();
angle+=0.3;
--------------void makeCube()-------------------
float P[8][3]={ {-1,-1, 1},{1,-1, 1},{1,1, 1},{-1,1, 1},
{-1,-1,-1},{1,-1,-1},{1,1,-1},{-1,1,-1}};
float * planes[6][4] ={ {P[0],P[1],P[2],P[3]},
{P[1],P[5],P[6],P[2]},
{P[4],P[7],P[6],P[5]},
{P[0],P[3],P[7],P[4]},
{P[3],P[2],P[6],P[7]},
{P[0],P[4],P[5],P[1]}};
int i;
for(i=0;i<6;i++){
float *normal;
normal = calcNormal(planes[i][0],planes[i][1],planes[i][2]);
glBegin(GL_QUADS);
glNormal3f(normal[0], normal[1], normal[2]);
glVertex3f(planes[i][0][0],planes[i][0][1],planes[i][0][2]);
glVertex3f(planes[i][1][0],planes[i][1][1],planes[i][1][2]);
glVertex3f(planes[i][2][0],planes[i][2][1],planes[i][2][2]);
glVertex3f(planes[i][3][0],planes[i][3][1],planes[i][3][2]);
glEnd();
}
----------------float* calcNormal()----------------------
float vec1[3] = {P2[0]-P1[0],P2[1]-P1[1],P2[2]-P1[2]};
float vec2[3] = {P3[0]-P2[0],P3[1]-P2[1],P3[2]-P2[2]};
float cross[3] = {vec1[1]*vec2[2]-vec2[1]*vec1[2],
vec1[2]*vec2[0]-vec2[2]*vec1[0],
vec1[0]*vec2[1]-vec2[0]*vec1[1]};
float modCross = sqrt(cross[0]*cross[0]+cross[1]*cross[1]+cross[2]*cross[2]);
cross[0]/=modCross;
cross[1]/=modCross;
cross[2]/=modCross;
return cross;
-------------resizeGL--------------------------
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
GLfloat x = GLfloat(width) / height;
glFrustum(-x, +x, -1.0, +1.0, 4.0, 15.0);
glMatrixMode(GL_MODELVIEW);
It seems that you're transforming the position of the light in your paintGL section.
Looking over old code, I found an app in my code directory that loads and rotates .OBJ meshes, while allowing the light to be moved.
I think that the solution is to set the position of the light each frame. (Can't remember it's been over 18 months since I touched the project)
void idleFunc()
{
light(); /// *** I think you need to replicate this functionality ****
glPushMatrix();
myGluLookAt(0.0, -.50, -6.0, /* eye is at (0,0,5) */
0.0, 0.0, 0.0, /* center is at (0,0,0) */
0.0, 1.0, 0.); /* up is in positive Y direction */
transformFunc();
displayFunc();
glPopMatrix();
}
void displayFunc()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
if (useDrawList)
glCallList(DLid);
else
drawObj(loadedObj);
drawLight0(); // *** just displays an unlit sphere at the position of the light **
glutSwapBuffers();
frameCount++;
}
/* set the poition of each of the lights */
void light()
{
glLightfv(GL_LIGHT0, GL_POSITION, lightPos1);
glLightfv(GL_LIGHT1, GL_POSITION, lightPos2);
}
i solved this problem drawing the cube with VERTEX ARRAYS rather than DIRECT MODE, it seems that rotations or lights affect the object in a different way with each method, which is quite weird
How can I have separate material properties for different objects drawn in OpenGL?
I did the following code, which apparently only shows the later colour:
//************** Object 1 **************
glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
glColor4f(149.0/255.0, 78.0/255.0, 22.0/255.0, 1.0);
float mat_specular[] = {0.992157, 0.941176, 0.807843, 1.0};
float shininess = 10;
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialf(GL_FRONT, GL_SHININESS, shininess);
glPushMatrix();
glTranslatef(0, 3.0, 0);
drawSphere(0.1, 0.1, 0.1);
glRotatef(10, 1, 0, 0);
glDisable(GL_COLOR_MATERIAL);
//************** Object 2 *****************
glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT, GL_DIFFUSE);
glColor4f(48.0/255.0, 48.0/255.0, 48.0/255.0, 1.0);
float mat_specular_2[] = {0.992157, 0.941176, 0.807843, 1.0};
float shininess_2 = 10;
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular_2);
glMaterialf(GL_FRONT, GL_SHININESS, shininess_2);
glPushMatrix();
glTranslatef(-0.6, 0.2, 1.6/2.0);
drawSphere(0.1, 0.1, 0.1);
glPopMatrix();
glDisable(GL_COLOR_MATERIAL);
When rendered, the colour set for the Object 2 is used for the entire scene. So the Object 1 is also rendered in Object 2's colour despite having its own colour set already.
How can I have the 2 objects to have separate material properties so that they can be displayed as different colours instead of just one colours in the whole scene?
You should put:
glEnable(GL_COLOR_MATERIAL);
As the first thing in your render function, then set the light parameters:
glDisable(GL_COLOR_MATERIAL);
glPushMatrix();
Then set the properties of the material and call the object. All the objects from now on will have this property, if you want to use another material on another object just type:
glDisable(GL_COLOR_MATERIAL);
again, before modeling the second object and so on. If you still have questions, just ask.
First, your example code looks reasonable and your objects should indeed have different materials.
But keep in mind that you only change the diffuse material color for your second object, as you set exactly the same specular colors and shininess values for both objects. And the ambient of the second object is also the same like for the first, as you only enable color material for the diffuse channel, so the ambient is unchanged from the first object, as OpenGL is a state machine.
So the only material difference between the objects is their diffuse color and this difference is (101, 30, 26). So can it be, that this difference is just outweighted by the ambient and specular terms that are completely equal and is therefore just too small for you to notice? Try completely different materials and see if there is really no difference.
It seems you have missed a glPopMatrix after drawing the first object. I don't know how that would change things.