如何用高效的用 shader 實現柱狀圖？

Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"

struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};

struct v2f
{
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
};

v2f vert (appdata v)
{
v2f o;
o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
o.uv = v.uv;
return o;
}

sampler2D _MainTex;
#define bars 32.0 // How many buckets to divide spectrum into
#define barSize 1.0 / bars // Constant to avoid division in main loop
#define barGap 0.1 * barSize // 0.1 represents gap on both sides, so a bar is
// shown to be 80% as wide as the spectrum it samples
#define sampleSize 0.02 // How accurately to sample spectrum, must be a factor of 1.0
// Setting this too low may crash your browser!

// Helper for intensityToColour
float h2rgb(float h)
{
if (h &< 0.0) h += 1.0; if (h &< 0.166666) return 0.1 + 4.8 * h; if (h &< 0.5) return 0.9; if (h &< 0.666666) return 0.1 + 4.8 * (0.666666 - h); return 0.1; } // Map [0, 1] to rgb using hues from [240, 0] - ie blue to red float3 intensityToColour(float i) { // Algorithm rearranged from http://www.w3.org/TR/css3-color/#hsl-color // with s = 0.8, l = 0.5 float h = 0.666666 - (i * 0.666666); return float3(h2rgb(h + 0.333333), h2rgb(h), h2rgb(h - 0.333333)); } float4 frag (v2f i) : SV_Target { float4 fragColor = tex2D(_MainTex, i.uv); // Map input coordinate to [0, 1) float2 uv = float2(i.uv.x, 1 - i.uv.y); // Get the starting x for this bar by rounding down float barStart = floor(uv.x * bars) / bars; // Discard pixels in the "gap" between bars if (uv.x - barStart &< barGap || uv.x &> barStart + barSize - barGap)
{
fragColor = (float4)0.0;
}
else
{
// Sample spectrum in bar area, keep cumulative total
float intensity = 0.0;
for (float s = 0.0; s &< barSize; s += barSize * sampleSize) { // Shader toy shows loudness at a given frequency at (f, 0) with the same value in all channels intensity += tex2D(_MainTex, float2(barStart + s, 0.0)).r; } intensity *= sampleSize; // Divide total by number of samples taken (which is 1 / sampleSize) intensity = clamp(intensity, 0.005, 1.0); // Show silent spectrum to be just poking out of the bottom // Only want to keep this pixel if it is lower (screenwise) than this bar is loud float i = float(intensity &> uv.y); // Casting a comparison to float sets i to 0.0 or 1.0

public class RandomDataTexture : MonoBehaviour {

const int NumData = 256;

public Texture2D texture;