I am using point sprites to display a few ten thousand points, each with a different size. It works well, looks great and is quite fast. I'm using a VBO with the coordinates and the sizes in it (4 floats per point).
Here is my display code
glEnable(GL_POINT_SPRITE_OES);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, pointTexture);
glTexEnvi( GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE );
glEnableClientState(GL_VERTEX_ARRAY);
glBindBuffer(GL_ARRAY_BUFFER, pointVertices);
glVertexPointer(3, GL_FLOAT, 4*sizeof(float), 0);
glEnableClientState(GL_POINT_SIZE_ARRAY_OES);
glPointSizePointerOES(GL_FLOAT,4*sizeof(float),(GLvoid*) (sizeof(GL_FLOAT)*3));
glDrawArrays(GL_POINTS, 0, pointNum);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glDisableClientState(GL_POINT_SIZE_ARRAY_OES);
glDisableClientState(GL_VERTEX_ARRAY);
glDisable(GL_TEXTURE_2D);
glDisable(GL_POINT_SPRITE_OES);
Now, I would also like to be able to zoom in, i.e. use glScalef. Is it possible to change the size of the points accordingly without updating the VBO? glPointSize doesn't have any effect, as I'm using GL_POINT_SIZE_ARRAY_OES.
Yes, use glPointParameter with the GL_POINT_DISTANCE_ATTENUATION parameter.
http://www.khronos.org/opengles/sdk/1.1/docs/man/glPointParameter.xml
It's quite tricky to get right, though.
Related
I'm using the following code to draw a green line at some specified coordinates
GLfloat colors[] = {0,1,0,1, 0,1,0,0.5};
CGPoint v[] = {{p1.x, p1.y}, {p2.x, p2.y}};
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_LINE_SMOOTH);
glLineWidth(10);
glVertexPointer(2, GL_FLOAT, 0, &v);
glColorPointer(4, GL_FLOAT, 0, &colors);
glDrawArrays(GL_LINE_LOOP, 0, 2);
glDisableClientState(GL_LINE_SMOOTH);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
The problem is that once in a while even if the draw method gets called, the line turns black or does not get drawn entirely. i've checked the coordinates i pass and they seem fine.
Is there something that i'm missing?
GL_LINE_SMOOTH has never been an acceptable argument to glEnableClientState().
It might not be the source of the problem, and you might have noticed it already, but isn't it correct to pass arrays to the functions without '&' or with '[0]'? i.e.
glVertexPointer(2, GL_FLOAT, 0, &v); // --> &v should be v, or &v[0]
glColorPointer(4, GL_FLOAT, 0, &colors); // --> colors, or &colors[0]
Also, glEnable(GL_LINE_SMOOTH); seems the correct syntax.
I´m creating an opengl ES project and I´m trying to show some textures, all works good but the problem is the use of the memory, every 5 seconds increments almost 1 Mb, I think I´m doing something wrong, I´m not using any of this apple recommendations I will tray for sure, but I want to know if my code have some bug, there is how I´m paiting:
// Generate the vertex buffer object (VBO)
glGenBuffers(1, &ui32Vbo);
// Bind the VBO so we can fill it with data
glBindBuffer(GL_ARRAY_BUFFER, ui32Vbo);
// Set the buffer's data
// Calculate verts size: (3 vertices * stride (3 GLfloats per each vertex))
glBufferData(GL_ARRAY_BUFFER, uiSize, verts, GL_STATIC_DRAW);
// Bind the VBO so we can fill it with data
glBindBuffer(GL_ARRAY_BUFFER, ui32Vbo);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 20, 0); // Stride = 20 bytes
glBindTexture(GL_TEXTURE_2D, textID);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 20, (void *)12);
glDrawArrays(GL_TRIANGLE_FAN, 4, 4);
// Bind the VBO so we can fill it with data
glBindBuffer(GL_ARRAY_BUFFER, 0);
Thank you very much!!!
You should generate the vertex buffer object only once, the use it draw.
It seems you create a new one each frame.
I have a game that renders a bunch of sprites (several hundred), almost all of which are using the same texture. Currently, I'm calling glDrawArrays(...) for each one, which I recently discovered was very inefficient. After doing some research, I've learned that I need to put all my vertices for every sprite into one big vertex buffer, and call glDrawArrays(...) just once using that. However, when I do so it only draws the first sprite, and the other 200 are blank.
blueSpriteVertices[blueBatchNum * 4] = Vertex3DMake(xloc, yloc, zloc);
blueSpriteVertices[blueBatchNum * 4 + 1] = Vertex3DMake(xloc + size, yloc, zloc);
blueSpriteVertices[blueBatchNum * 4 + 2] = Vertex3DMake(xloc, yloc + size, zloc);
blueSpriteVertices[blueBatchNum * 4 + 3] = Vertex3DMake(xloc + size, yloc + size, zloc);
blueBatchNum++;
//^^This block of code^^ is called iteratively, adding data for various sprites
//(around 200) to the vertex array. "xloc", "yloc", etc. are private members of
//this sprite class
//Draw the whole batch
glEnableClientState(GL_VERTEX_ARRAY);
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glColor4f(1, 1, 1, 1);
//This code is actually in the Texture2D class implementation, hence "_name"
//and "coordinates"
glBindTexture(GL_TEXTURE_2D, _name);
glVertexPointer(3, GL_FLOAT, 0, blueSpriteVertices);
glTexCoordPointer(2, GL_FLOAT, 0, coordinates);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_2D);
glDisableClientState(GL_VERTEX_ARRAY);
I finally solved this problem by using GL_TRIANGLES instead of GL_TRIANGLE_STRIP, and handled the triangle strips manually. By doing so I was able to eliminate all the "strips" that it was interpreting in between my sprites. Works like a charm now, and the batching definitely improved my game's performance astronomically.
Using (GL_TRIANGLES instead of GL_TRIANGLE_STRIP works for me (on Android)
glDrawElements(GL_TRIANGLES, 6 * mSpriteCounter, GL_UNSIGNED_SHORT, (char*) NULL);
The glDrawArrays() last parameter should contain the number of vertices (in your case you have only 4). Also you must have the same number of texture coordinates to match the drawn vertices!
I have a set of textures which I need to draw at different vertices such that every texture is visible.I cannot define a static set of vertices since I load the textures dynamically and I dont know how many textures will be loaded everytime ( i choose them based on a condition).
This is how my code looks as of now.
for(int i=0;i<num_img;i++)
{
glLoadIdentity();
glTranslatef(0.0, 0.0, -3.0);
glRotatef(rot, 1.0, 1.0, 1.0);
glBindTexture(GL_TEXTURE_2D, texture[i]);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glNormalPointer(GL_FLOAT, 0, normals);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}
Is there anyway to dynamically generate vertices that can be passed as final argument of glVertexPointer() ?
Do you know the maximum number of vertices that you will use? Maybe you could create the vertices array to be that maximum size then in the first parameter of glVertexPointer you only pass the number of vertices that you actually use.
I'm working on an iPhone project in Xcode 3.2.4 for which I'd like to display textures using OpenGL ES 2.0. I don't have much previous experience working with OpenGL, but so far it doesn't seem too awful. So far I've mainly been referring to The OpenGL ES 2.0 Programming Guide (gold book).
Right now I've got a project based on Xcode's default OpenGL template, with the drawFrame function replaced with my texture-displaying code, which in turn is based on the Simple_Texture2D project from the gold book. However, the square I should be drawing my texture onto does not display it; it's black instead, and I'm not sure why this is happening.
Here are the contents of drawFrame:
[(EAGLView *)self.view setFramebuffer];
GLuint textureID;
static const GLfloat squareVertices[] =
{
-0.5f, -0.33f,
0.5f, -0.33f,
-0.5f, 0.33f,
0.5f, 0.33f
};
// Generate a 2 x 2 rgb image at 3 bytes per pixel.
GLubyte image[4 * 3] =
{
255, 0, 0,
0, 255, 0,
0, 0, 255,
255, 255, 0
};
glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, squareVertices);
glEnableVertexAttribArray(ATTRIB_VERTEX);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
GLushort indices[] = {0, 1, 2, 3, 2, 1};
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
[(EAGLView *)self.view presentFramebuffer];
Perhaps to an experienced OpenGL user it'll be obvious what I'm doing wrong. Otherwise, any suggestions, guesses, or constructive comments of any kind are great too.
Thanks in advance!
You need not only vertex positions but also texture coordinates. As it stands you're only specifying vertex positions, so you're only going to vertices with whatever color was set last, no texture.
Try setting up a texCoord array and doing another glVertexAttribPointer(ATTRIB_TEXCOORD, ...) and a glEnableVertexArray(ATTRIB_TEXCOORD).
(If you're lighting you may want normals as well.)
There's sample code off songho's OpenGL Vertex Array page (glDrawElements section). See the draw3 function and prior setup.
Note that vertex buffer objects (and other buffer objects) are generally replacing vertex arrays (and other arrays) as the preferred solution for rendering batches of data at once. VBOs have more opportunity to be stored in a high-performance way by the driver.