如何在 XNA 中移动 3d 对象? [英] how to move 3d object in XNA?

问题描述

我想移动一个 3d 汽车模型，当我按下向左或向右箭头键时，我改变了角度，当我按下向上箭头时，汽车就会行驶.

I want to move a 3d car model, when I press the left or right arrow key I change the angle, when I press the up arrow the car drives.

这是更新方法中的代码:

This is the code in the update method:

float dirX = (float)Math.Sin(angle);
float dirY = (float)Math.Cos(angle);

if (Keyboard.GetState().IsKeyDown(Keys.Up))
        {
            position += new Vector3(-dirX, dirY, 0);

            if (Keyboard.GetState().IsKeyDown(Keys.Left))
            {
                angle += 0.015f;
            }

            if (Keyboard.GetState().IsKeyDown(Keys.Right))
            {
                angle -= 0.015f;
            }
        }

这是计算部分，但显然我还需要在屏幕上移动汽车.我想让汽车向前移动，而不是向上移动，所以我想我应该在 X 轴上将它旋转 90 度，而且我想在按向左或向右键时旋转汽车.

This is the calculating part, but obviously I also need to move the car on the screen. I want the car to move forward, not up, so I thought I should rotate it 90 degrees on the X axis, and also I want to rotate the car when I press the left or right keys.

我写了这段代码:

world = Matrix.CreateTranslation(position) * Matrix.CreateRotationY(angle) * Matrix.CreateFromAxisAngle(Vector3.UnitX, MathHelper.ToRadians(-90));

此代码无效，谁能告诉我如何移动它?

This code isn't working, can anybody tell me how can I move it?

推荐答案

您应该意识到您的 Y 轴实际上是向上"，而不是向前"(按照惯例).虽然此问题有很多解决方案，但解决您的问题的最快方法是:

You should be aware that your Y axis is actually "up", not "forward" (by conventions). While this problem has many solutions, quickest way to fix yours is that:

float dirX = (float)Math.Sin(angle);
float dirZ = (float)Math.Cos(angle);

position += new Vector3(dirX, 0, dirZ); 

然后，您应该以正确的顺序将变换矩阵相乘:

Then, you should multiply your transformation matrices in the correct order:

Scale * Rotation * Translation

在你的情况下翻译成:

// this will rotate car around the Y axis, and then translate it to correct location
world = Matrix.CreateRotationY(angle) * Matrix.CreateTranslation(position);

一个建议，按照A-Type的建议去做，使用方向*速度.

One suggestion, do as A-Type suggested, and use direction * speed.

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