Making a grid on iPhone using Opengl
- by TheGambler
I'm trying to make a grid similar to what you would see in these geo games(geoDefense/geometry wars). I'm wanting to apply separate transformation matrixes to each to create different effects. So, it makes since to me that I need to draw each square separately to that I can apply a different transformation to each one.
The problem I'm having is mapping these grids out or connecting the squares. The coordinate systems is still confusing to me. I know it would be easy just to create a huge triangle strip but I'm not able to figure out a way to apply separate transformations to each square( quad ) if I use triangle strips. So first question:
Can you apply different transformations to quads if you use a triangle strip to draw a huge grid? If so, any tips suggestions on how to do so?
If not, how does one usually connect textures without using triangle strips?
Here is my coord setup:
const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0;
GLfloat size;
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);
CGRect rect = view.bounds;
glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size /
(rect.size.width / rect.size.height), zNear, zFar);
glViewport(0, 0, rect.size.width, rect.size.height);
Here is my draw:
- (void)drawView:(GLView*)view;
{
int loop;
//glColor4f(1.0, 1.0, 1.0, 0.5);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//Grid Loop
for( loop = 0; loop < kNumberSectionsInGrid; loop++ )
{
//glLoadIdentity();
static Matrix3D shearMatrix;
Matrix3DSetShear(shearMatrix, 0.2, 0.2);
static Matrix3D finalMatrix;
//Matrix3DMultiply(temp2Matrix, shearMatrix, finalMatrix);
glLoadMatrixf(shearMatrix);
glTranslatef(-1.0f,(float)loop,-3.0f);
glScalef(0.1, 0.1, 0.0);
Vertex3D vertices[] = {
{-1.0, 1.0, 0.5},
{ 1.0, 1.0, 0.5},
{ -1.0, -1.0, 0.5},
{ 1.0, -1.0, 0.5}
};
static const Vector3D normals[] = {
{0.0, 0.0, 1.0},
{0.0, 0.0, 1.0},
{0.0, 0.0, 1.0},
{0.0, 0.0, 1.0},
};
GLfloat texCoords[] = {
0.0, 1.0,
1.0, 1.0,
0.0, 0.0,
1.0, 0.0
};
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glNormalPointer(GL_FLOAT, 0, normals);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}
}
glMatrixMode(GL_MODELVIEW);
