VP矩阵以及GL.GetGPUProjectionMatrix

就当笔记吧 / 2023-05-06 / 原文

c#层的VP矩阵

public class VPMatrixTest : MonoBehaviour
{

    void Start()
    {
        var mainCam = Camera.main;

        var viewMatrix = mainCam.worldToCameraMatrix;
        Debug.Log($"viewMatrix:\n {viewMatrix}");

        var projMatrix = mainCam.projectionMatrix;
        Debug.Log($"projMatrix:\n {projMatrix}");

        var projMatrix2 = GL.GetGPUProjectionMatrix(projMatrix, false);
        Debug.Log($"projMatrix2:\n {projMatrix2}");

        var projMatrix3 = GL.GetGPUProjectionMatrix(projMatrix, true);
        Debug.Log($"projMatrix3:\n {projMatrix3}");

        var vpMatrix = projMatrix2 * viewMatrix;
        Debug.Log($"vpMatrix:\n {vpMatrix}");
    }

}

GetGPUProjectionMatrix的第二个参数为false(proj2Matrix)和true(proj3Matrix)的差别是m11一个为正，一个为负。

所以第2个参数名叫flipVertical会不会更容易理解?

shader层的VP矩阵

需要用Frame Debug来看(Window -> Analysis -> Frame Debugger)

Shader "My/MVPMatrix/VpMatrix"
{
    SubShader
    {
        Tags { "RenderType" = "Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float4 vMatrix : TEXCOORD0;
                float4 pMatrix : TEXCOORD1;
            };

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);

                o.vMatrix = mul(UNITY_MATRIX_V, v.vertex); //矩阵乘法结果无意义, 仅仅测试用
                o.pMatrix = mul(UNITY_MATRIX_P, v.vertex);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                return fixed4(1, 1, 1, 1);
            }

            ENDCG
        }

    }
}