1.shadertoy 近大远小效果

//用面积算,因为绘制得依赖uv坐标，所以必须把屏幕考虑进去
float DistLine(vec3 ballPos,vec3 screen,vec3 camPos)
{
    return length(cross(camPos - ballPos,screen)) / length(screen);
}
//用距离算
float CamDist(vec3 ballPos,vec3 camPos)
{
    return length(camPos - ballPos);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord.xy / iResolution.xy;
    uv -= 0.5;

    //将uv的x坐标进行放大
    uv.x *= iResolution.x / iResolution.y;

    vec3 ballPos = vec3(0.0,0.0,-2.0);
    vec3 screen = vec3(uv.x,uv.y,0.0) - ballPos;

    float t = iTime;
    //旋转摄像机
    vec3 camPos = vec3(sin(t),0.0,1.0 + cos(t));

    //近大远小
    float d = DistLine(ballPos,screen,camPos) * 0.5;
    d = smoothstep(0.10,0.09,d);

    fragColor = vec4(d);
}

效果:

2.unity 旋转摄像机

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RotCam : MonoBehaviour
{
    private float angle = 15;
    private Vector3 axis = new Vector3(0,1,0);
    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        //transform.RotateAround(Vector3.zero, axis, angle * Time.deltaTime);
        float t = Time.time;
        transform.position = new Vector3(Mathf.Sin(t) * 15,0,Mathf.Cos(t) * 15 - 35);
    }
}