partially done work on total source tree rework, separation of engine context and game context, generalization of renderer for different backends as well as web platform target

src/rendering/twn_triangles.c

@@ -0,0 +1,81 @@
+#include "twn_rendering_c.h"
+#include "twn_context.h"
+#include "twn_textures_c.h"
+#include "twn_rendering_platform.h"
+
+#include <stb_ds.h>
+
+
+/* TODO: automatic handling of repeating textures */
+/*       for that we could allocate a loner texture */
+void unfurl_triangle(const char *path,
+                     t_fvec3 v0,
+                     t_fvec3 v1,
+                     t_fvec3 v2,
+                     t_shvec2 uv0,
+                     t_shvec2 uv1,
+                     t_shvec2 uv2)
+{
+    const t_texture_key texture_key = textures_get_key(&ctx.texture_cache, path);
+
+    struct mesh_batch_item *batch_p = hmgetp_null(ctx.uncolored_mesh_batches, texture_key);
+    if (!batch_p) {
+        struct mesh_batch item = {0};
+        hmput(ctx.uncolored_mesh_batches, texture_key, item);
+        batch_p = &ctx.uncolored_mesh_batches[hmlenu(ctx.uncolored_mesh_batches) - 1]; /* TODO: can last index be used? */
+    }
+
+    union uncolored_space_triangle triangle = { .primitive = {
+        .v0 = v0,
+        .v1 = v1,
+        .v2 = v2,
+        .uv1 = m_to_fvec2(uv1),
+        .uv0 = m_to_fvec2(uv0),
+        .uv2 = m_to_fvec2(uv2),
+    }};
+
+    union uncolored_space_triangle *triangles = (union uncolored_space_triangle *)batch_p->value.primitives;
+
+    arrpush(triangles, triangle);
+    batch_p->value.primitives = (uint8_t *)triangles;
+}
+
+
+void draw_uncolored_space_traingle_batch(struct mesh_batch *batch,
+                                         t_texture_key texture_key)
+{
+    static vertex_buffer vertex_array = 0;
+    if (vertex_array == 0)
+        vertex_array = create_vertex_buffer();
+
+    const size_t primitives_len = arrlenu(batch->primitives);
+
+    /* nothing to do */
+    if (primitives_len == 0)
+        return;
+
+    const t_frect srcrect = textures_get_srcrect(&ctx.texture_cache, texture_key);
+    const t_frect dims    = textures_get_dims(&ctx.texture_cache, texture_key);
+
+    const float wr = srcrect.w / dims.w;
+    const float hr = srcrect.h / dims.h;
+    const float xr = srcrect.x / dims.w;
+    const float yr = srcrect.y / dims.h;
+
+    /* update pixel-based uvs to correspond with texture atlases */
+    for (size_t i = 0; i < primitives_len; ++i) {
+        struct uncolored_space_triangle_payload *payload =
+            &((union uncolored_space_triangle *)batch->primitives)[i].payload;
+
+        payload->uv0.x = xr + ((float)payload->uv0.x / srcrect.w) * wr;
+        payload->uv0.y = yr + ((float)payload->uv0.y / srcrect.h) * hr;
+        payload->uv1.x = xr + ((float)payload->uv1.x / srcrect.w) * wr;
+        payload->uv1.y = yr + ((float)payload->uv1.y / srcrect.h) * hr;
+        payload->uv2.x = xr + ((float)payload->uv2.x / srcrect.w) * wr;
+        payload->uv2.y = yr + ((float)payload->uv2.y / srcrect.h) * hr;
+    }
+
+    specify_vertex_buffer(vertex_array, batch->primitives, primitives_len * sizeof (struct uncolored_space_triangle_payload));
+
+    finally_draw_uncolored_space_traingle_batch(batch, texture_key, vertex_array);
+}