From 1ae1b370da0ce0cf8501b9e6be8c6ac25e249e1a Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Wed, 31 Dec 2025 14:46:33 -0800
Subject: Initial texturing changes

---
 src/swgfx.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 49 insertions(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/swgfx.c b/src/swgfx.c
index c298fb4..612f82d 100644
--- a/src/swgfx.c
+++ b/src/swgfx.c
@@ -46,6 +46,9 @@ typedef struct swgfx {
   // before rendering the model's triangles.
   sgMat4       viewProj; // View-projection matrix.
   sgMat4       mvp;      // Model-view-projection matrix.
+  const sgTexture_t* texture;// User-specified texture.
+  sgTexture_t        defaultTexture; // A default for when no texture is provided.
+  sgPixel            defaultPixel;   // The single-pixel of the default texture.
 } swgfx;
 
 static inline R   rmin(R   a, R   b) { return (a <= b) ? a : b; }
@@ -265,6 +268,22 @@ void SetDepth(swgfx* gfx, const sgVec2i p, R depth) {
   *Depth(gfx, p.x, p.y) = depth;
 }
 
+// TODO: Mipmapping.
+sgPixel Sample(const sgTexture_t* texture, sgVec2 uv) {
+  assert(texture);
+  assert(texture->pixels);
+  // TODO: (1/2, 1/2) is the center of the pixel. Do we need to do something
+  //  about it here?
+#define INDEX(X,Y) texture->pixels[(Y) * texture->width + (X)]
+  // Doing a nearest sample for now. TODO: Other sampling strategies.
+  const int x = (int)(uv.x * (R)texture->width);
+  const int y = (int)(uv.y * (R)texture->height);
+  // Repeat for now. TODO: Clamping and other strategies.
+  const int xx = x % texture->width;
+  const int yy = y % texture->height;
+  return INDEX(xx,yy);
+}
+
 static inline sgAABB2 TriangleAabb2(sgVec2 p0, sgVec2 p1, sgVec2 p2) {
   return (sgAABB2){.pmin = min2(min2(p0, p1), p2),
                    .pmax = max2(max2(p0, p1), p2)};
@@ -340,12 +359,16 @@ static void DrawTriangle2(swgfx* gfx, const sgTri3* const tri) {
         R* depth = Depth(gfx, x, y);
         if ((0.f <= z) && (z <= 1.f) && (z <= *depth)) {
           *depth = z;
-          const sgVec3 depths = (sgVec3){tri->p0.pos.z, tri->p1.pos.z, tri->p2.pos.z};
-          const sgVec2  uv = PerspectiveInterp2(bar, depths, z, tri->p0.uv, tri->p1.uv, tri->p2.uv);
-          const int r = (int)(uv.x * 255.f);
+          const sgVec3  depths = (sgVec3){tri->p0.pos.z, tri->p1.pos.z, tri->p2.pos.z};
+          const sgVec2  uv     = PerspectiveInterp2(bar, depths, z, tri->p0.uv, tri->p1.uv, tri->p2.uv);
+          const sgPixel colour = Sample(gfx->texture, uv);
+          //const sgPixel colour = (sgPixel){255, 0, 255, 255};
+          // TODO: When doing lighting, need to tone-map here.
+          /*const int r = (int)(uv.x * 255.f);
           const int g = (int)(uv.y * 255.f);
-          const sgVec2i pix = (sgVec2i){(int)x, (int)y};
-          SetPixel(gfx, pix, (sgPixel){r, g, 255, 255});
+          const sgPixel colour = (sgPixel){r, g, 255, 255};*/
+          const sgVec2i pix = (sgVec2i){x,y};
+          SetPixel(gfx, pix, colour);
         }
       }
     }
@@ -436,6 +459,12 @@ swgfx* sgNew(int width, int height, void* mem) {
   gfx->dims   = (sgVec2i){width, height};
   gfx->colour = SG_ALLOC(&aligned, width * height, sgPixel);
   gfx->depth  = SG_ALLOC(&aligned, width * height, R);
+  gfx->defaultPixel   = (sgPixel){255, 255, 255, 255};
+  gfx->defaultTexture = (sgTexture_t){
+    .width  = 1,
+    .height = 1,
+    .pixels = &gfx->defaultPixel,
+  };
   return gfx;
 }
 
@@ -446,7 +475,7 @@ void sgDel(swgfx** ppSwgfx) {
   }
 }
 
-void sgPresent(swgfx* gfx, sgVec2i dimensions, sgPixel* screen) {
+void sgPresent(swgfx* gfx, sgVec2i dimensions, sgScreenPixel* screen) {
   assert(gfx);
   assert(screen);
   // Integer scaling only.
@@ -457,16 +486,18 @@ void sgPresent(swgfx* gfx, sgVec2i dimensions, sgPixel* screen) {
   const int sy = dimensions.y / gfx->dims.y;
 
   const sgPixel* src = gfx->colour;
-        sgPixel* dst = screen;
 
-  // Replicate each row 'sy' times.
   for (int y = 0; y < gfx->dims.y; ++y, src += gfx->dims.x) {
-    for (int yy = y*sy; yy < (y+1)*sy; ++yy) {
-      // Replicate each column 'sx' times.
+    // Replicate each row 'sy' times.
+    for (int yy = 0; yy < sy; ++yy) {
       const sgPixel* src_col = src;
       for (int x = 0; x < gfx->dims.x; ++x, ++src_col) {
-        for (int xx = x*sx; xx < (x+1)*sx; ++xx, ++dst) {
-          *dst = *src_col;
+        // Replicate each column 'sx' times.
+        for (int xx = 0; xx < sx; ++xx, ++screen) {
+          screen->r = src_col->r;
+          screen->g = src_col->g;
+          screen->b = src_col->b;
+          screen->a = src_col->a;
         }
       }
     }
@@ -518,6 +549,12 @@ void sgViewport(swgfx* gfx, int x0, int y0, int width, int height) {
   gfx->viewport = (sgViewport_t){x0, y0, width, height};
 }
 
+void sgTexture(swgfx* gfx, const sgTexture_t* texture) {
+  assert(gfx);
+  assert(texture);
+  gfx->texture = texture;
+}
+
 void sgClear(swgfx* gfx) {
   assert(gfx);
   const int N = gfx->dims.x * gfx->dims.y;
-- 
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