added linear interpolation in image to use it at the terrain generation

[demo] / src / image.cc

diff --git a/src/image.cc b/src/image.cc
index a99f75a..82d8cd1 100644 (file)
--- a/src/image.cc
+++ b/src/image.cc
@@ -121,11 +121,8 @@ bool Image::load(const char *fname)
        return true;
 }
 
-Vec4 Image::lookup_nearest(float u, float v) const
+Vec4 Image::get_pixel(int x, int y) const
 {
-       int x = (int)(u * w) % w;
-       int y = (int)(v * h) % h;
-
        if(is_float) {
                return ((Vec4*)pixels)[y * w + x];
        }
@@ -138,4 +135,40 @@ Vec4 Image::lookup_nearest(float u, float v) const
        color.w = pptr[3] / 255.0;
 
        return color;
+}
+
+Vec4 Image::lookup_nearest(float u, float v) const
+{
+       int x = (int)(u * w) % w;
+       int y = (int)(v * h) % h;
+
+       return get_pixel(x, y);
+}
+
+Vec4 Image::lookup_linear(float u, float v, float du, float dv) const
+{
+       /* bottom left */
+       int x0 = (int)(u * w) % w;
+       int y0 = (int)(v * h) % h;
+       int x1 = (x0 + 1) % w;
+       int y1 = (y0 + 1) % h;
+
+       /* uv coordinates at the img corners */
+       float u0 = (float)x0 / (float)w;
+       float v0 = (float)y0 / (float)h;
+       float u1 = (float)(x0 + 1) / (float)w;
+       float v1 = (float)(y0 + 1) / (float)h;
+
+       float tu = (u - u0) / (u1 - u0);
+       float tv = (v - v0) / (v1 - v0);
+
+       Vec4 p00 = get_pixel(x0, y0);
+       Vec4 p01 = get_pixel(x0, y1);
+       Vec4 p11 = get_pixel(x1, y1);
+       Vec4 p10 = get_pixel(x1, y0); 
+
+       Vec4 ptop = lerp(p01, p11, tu);
+       Vec4 pbot = lerp(p00, p10, tu);
+
+       return lerp(pbot, ptop, tv);
 }
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