Hello everyone. First time XNA project here, so still learning the ropes.

My first idea for a starter project was to make a tile based game. Each movable terrain square would be one quad (or 2 triangles).

Then use some method to determine which tile the mouse is over and clicking it moves the player there.

So what would be the ideal way to do this in XNA? My first thought was to create a triangle strip and a text file with all the vertices and heights and load it in and draw it.

Any other suggestions?

I'm not familiar with XNA, so have no code but do have some input.

1) procedurally generate a grid of vertices such that there are m+1 * n+1 verts, where m and n are the dimensions of your terrain in quads.

2) Why strips over lists? While strips make sense as a performance standpoint, that has really not been an issue for years.I use lists for everything.

3) As long as your terrain doesn't include overhangs, a simple height map is all that is required.(use a gray scale texture with same dimensions as your grid))

4) Use your heightmap to get the height at each vertices.

5) picking is what your looking for( how to determine what your mouse is clicking) use the mouse coords, unproject them to crate a ray from camera position. Intersect that ray with your triangles, that tells you which tile is hit, and which tile your unit should move to.

There is a long road ahead, but it's been done by others before, keep at it and you will succeed!

Ok cheers for the tips. I only chose triangle strip because I thought it was more efficient at drawing triangles. That was what they taught us at university anyway, but that was a long time ago. Haven't really done any game programming since I finished - this is my first foot back in the water.

Are there any tutorials on drawing triangle lists? Or some jumping-in-to-xna guides? I tried following the MSDN tutorials but they seem to miss out key important parts to get things done that a fresh person to XNA wouldn't have any idea about.

Edit: This is what I've come up with so far but its not drawing anything.

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;

namespace RO3
{

    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        Matrix worldMatrix;
        Matrix viewMatrix;
        Matrix projectionMatrix;

        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        GraphicsDevice device;
        Effect basicEffect;

        VertexPositionColor[] primitiveList;

        int points = 8;
        short[] triangleListIndices;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        protected override void Initialize()
        {
            graphics.PreferredBackBufferWidth = 1000;
            graphics.PreferredBackBufferHeight = 1000;
            graphics.IsFullScreen = false;
            graphics.ApplyChanges();
            Window.Title = "RO3";

            InitializeTransform();
            InitializeTriangleList();

            base.Initialize();
        }

        protected override void LoadContent()
        {
            device = graphics.GraphicsDevice;
            basicEffect = Content.Load<Effect>("effects");
        }

        private void InitializeTransform()
        {
            worldMatrix = Matrix.CreateTranslation(new Vector3(-1.5f, -0.5f, 0.0f));

            viewMatrix = Matrix.CreateLookAt(
                new Vector3(0.0f, 0.0f, 1.0f),
                Vector3.Zero,
                Vector3.Up
                );

            projectionMatrix = Matrix.CreateOrthographicOffCenter(
                0,
                (float)GraphicsDevice.Viewport.Width,
                (float)GraphicsDevice.Viewport.Height,
                0,
                1.0f, 1000.0f);
        }


        private void InitializeTriangleList()
        {
            primitiveList = new VertexPositionColor[points];

            for (int x = 0; x < points / 2; x++)
            {
                for (int y = 0; y < 2; y++)
                {
                    primitiveList[(x * 2) + y] = new VertexPositionColor(new Vector3(x * 100, y * 100, 0), Color.White);
                }
            }

            triangleListIndices = new short[18] { 0, 1, 2, 2, 1, 3, 2, 3, 4, 4, 3, 5, 4, 5, 6, 6, 5, 7 };
        }

        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        protected override void Update(GameTime gameTime)
        {
            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            device.Clear(Color.DarkSlateBlue);

            basicEffect.CurrentTechnique = basicEffect.Techniques["ColoredNoShading"];
            foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
            {
                pass.Apply();

            }

            RasterizerState rs = new RasterizerState();
            rs.CullMode = CullMode.None;
            device.RasterizerState = rs;

            //drawing code goes after this

            DrawTriangleList();


            base.Draw(gameTime);
        }

        private void DrawTriangleList()
        {
            GraphicsDevice.DrawUserIndexedPrimitives<VertexPositionColor>(
                PrimitiveType.TriangleList,
                primitiveList,
                0,   // vertex buffer offset to add to each element of the index buffer
                8,   // number of vertices to draw
                triangleListIndices,
                0,   // first index element to read
                6    // number of primitives to draw
            );
        }
    }
}

2) Why strips over lists? While strips make sense as a performance standpoint,

No. They don't. They are actually horribly inefficient in terrain rendering.

Think about it. With strips, you are always reusing last two vertices for current triangle.

With a triangle list of the terrain heightmap, it is possible (I know, because I implemented it) to create a shape that for a 100x100 grid (20,000 tris) executes Vertex Shader only 056*20,000 times - simply because it reuses the vertices that are in post-transform vertex cache and keeps the cache warm with last 24 vertices all the time. The variant with 0.67*20,000 is easier to code, though.

With TriStrip, the best you can get is 1.01 *20,0000

As the OP said, I'm just reiterating what I have been told in the past. Paraphrasing here: "Strips are faster than lists, but in today's hardware, the difference is negligible."

Not to derail the OP's thread, but I was assuming the use of indexed geometry, and after reading your other reply, I thought that may have been the sticking point. As you said, using indexed geometry enables the post transform cache, reusing 2 vertices results in only a single xecution of the vertex shader for each triangle after the first, per row of quads. However upon doing the math, I see 202 shader executions per row of quads by 100 rows = 20200, or as you put it, 1.01 * 20000.

After unfurrowing my brow, I end up with the same count for lists. Could you explain a bit more in depth how lists are faster than strips, specifically how you arrived at the other 2 figures you gave for the naive and optimized list method?

Triangle strips are a major pain in the ass, especially when you're programatically generating geometry. Don't use them.

Depending on how you generate the terrain, it may be faster to just generate it each time the game loads rather than loading it from a file. I have a demo that uses opencl to generate terrain, and it can generate terrain an order of magnitude faster than it would take to load said terrain from disk.

For figuring out which triangle the mouse is mousing over, check this out.

http://xbox.create.msdn.com/en-US/education/catalog/sample/picking_triangle

You can basically copypaste their code for it.

The plan was to draw a 256x256 map, and have a "portal" somewhere on the map that leads to another map. So loading all the maps when the game loads is out of the question.

My plan was to have a text file for each map with a whole bunch of vertices, followed by objects on the map with a position to draw it at.

map1.map, "Home Town";

0,1,0,3,1,0,0,4,3,5,6,2,0,2,3,8,4,2,0,28,169,474,935,742,42,36;

"House.obj", 56,0,56;
"Car.obj", 56,0,80;

I have absolutely no idea how XNA loads objects, but this was my thought on how to do it.

Edit: Oh, and didn't need collision detection as I was just going to define each tile as walkable or not-walkable.

Does this sound like a reasonable, efficient way to draw a map?

Edit2: Actually, since the maps will all be 256x256, there's really no point in storing the x and z vertices in a text file since they will all be quads (tiles). The only thing that needs to be stored is the height of each group of 3 vertices. Which I suppose could be done with a height map image?