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Mooncinder

OpenGL Using vertices stored in a text file

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Mooncinder    145
Hey everyone, I'm a student studying games computing and for my latest assignment, I've been asked to write a program using OpenGL that will render a 3D model from a set of vertex values that are stored in a text file (originally from a VRML file). As we only started on OpenGL this year, I'm fairly new to it. I've managed to read the contents of the text file, edit it and output the data into another text file but I'm stuck on how to display the model from the text file. Maybe I'm just very unobservant but I've looked on opengl.org and I've tried going through several tutorials but none of them cover what I want to do. If anyone could point me in the right direction with this, it would be a great help. Thanks in advance, Mooncinder [Edited by - Mooncinder on April 18, 2006 12:58:06 PM]

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matthughson    588
Just draw it like you would any other triangle strip. You have all the vertex data, so now you just need to put it into a vertex array, and render.

I don't really use OGL, so hopefully someone else can give you some code samples if you are unsure of what I'm talking about.

Matt

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Mooncinder    145
Thanks for replying, Matt. I know it's a vertex array that I need, I'm just not sure how to take the vertices from the text file. In all the examples I've looked at so far, they just link to a long list of vertices elsewhere in the code.

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matthughson    588
Ah ok. In your original post it sounded like you had read all the vertex data in from the file already. Not the case? Or is it that you have the vertex data stored in an array, and you just aren't sure how to move that data from an array into a vertex array?

Matt

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Mooncinder    145
I'm sorry if my original post was confusing. I think I'm confusing myself!

What my program does is read a long list of numbers from a text file, format the data into vertices by adding curly brackets around each set of three numbers and then outputs the changed data into another text file. Is there a way I can read the data straight from the second text file into a vertex array?

Thanks for your help so far,
Mooncinder

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NickGravelyn    855
Well, to get your data into a huge array where you could use vertex array examples, it could be as easy as something like this:

#include <stdio.h>

//takes the filename and pointer to float array
//where the final vertices are stored
void ReadFile(const char *filename, float *vertices)
{
FILE *inFile;
if((inFile = fopen(filename,"rt")) == NULL)
{
//failed to open file. do errors and such
}

int vertCounter = 0;
char line[256];
float a, b, c;

while(!feof(inFile))
{
//get the next line of the file
fgets(line, 256, inFile);

//if it's a vertex, we store it
if(sscanf(line, "{%f, %f, %f}", &a, &b, &c) == 3)
{
vertices[vertCounter++] = a;
vertices[vertCounter++] = b;
vertices[vertCounter++] = c;
}
}

fclose(inFile);
}



Of course be sure that your incoming array can hold all the vertices or you'll end up in trouble, but that should work. Of course, it's not tested, but it looks good to me.

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