From 014077c89bb3c50718d56430f387109ad43508b6 Mon Sep 17 00:00:00 2001
From: quou <quou@disroot.org>
Date: Mon, 13 Jan 2025 20:56:13 +1100
Subject: basic picking and debug rendering

---
 model.cpp | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 71 insertions(+), 7 deletions(-)

(limited to 'model.cpp')

diff --git a/model.cpp b/model.cpp
index 9e78b19..03a24e0 100644
--- a/model.cpp
+++ b/model.cpp
@@ -9,6 +9,8 @@ extern "C" {
 }
 
 #include <string.h>
+#include <stdio.h>
+#include <algorithm>
 
 struct MVP_Cbuffer {
 	m4f model;
@@ -273,7 +275,7 @@ m4f Camera::get_proj() const {
 	return m4f::pers(fov, asp, near, far);
 }
 
-void Model_Instance::init(Device* dev, Model* model) {
+void Model_Instance::init(Device* dev, Heap* h, Model* model) {
 	m = model;
 	mvp = dev->create_buffer(
 		"Model instance MVP",
@@ -287,11 +289,26 @@ void Model_Instance::init(Device* dev, Model* model) {
 		Buffer_Flags::constant_buffer |
 		Buffer_Flags::cpu_readwrite
 	);
+	bounds = (AABB*)heap_alloc(
+		h,
+		sizeof *bounds * model->mesh_count
+	);
 }
 
-void Model_Instance::destroy(Device* dev) {
+void Model_Instance::destroy(Device* dev, Heap* h) {
 	dev->destroy_buffer(mat);
 	dev->destroy_buffer(mvp);
+	heap_free(h, bounds);
+}
+
+void Model_Instance::update() {
+	Mesh* meshes = m->get_meshes();
+	int i, c = m->mesh_count;
+	for (i = 0; i < c; i++)
+		bounds[i] = m4f::transform(
+			transform * meshes[i].world,
+			meshes[i].bound
+		);
 }
 
 void Model_Instance::update_cbuffers(
@@ -400,12 +417,34 @@ void Model_Instance::render(
 	}
 }
 
+int Model_Instance::pick(const v3f& o, const v3f& d) {
+	int i, c = m->mesh_count;
+	for (i = 0; i < c; i++) {
+		AABB& b = bounds[i];
+		v3f id = 1.0f / d;
+		v3f t1 = (b.min - o) * id;
+		v3f t2 = (b.max - o) * id;
+		float tmin = std::max(std::max(std::min(t1.x, t2.x), std::min(t1.y, t2.y)), std::min(t1.z, t2.z));
+		float tmax = std::min(std::min(std::max(t1.x, t2.x), std::max(t1.y, t2.y)), std::max(t1.z, t2.z));
+		if (tmax < 0.0f || tmin > tmax)
+		{
+			continue;
+		}
+		return i;
+	}
+	return -1;
+}
+
 void Model_Scene::init(
 	Arena* arena,
 	int max_instances,
 	Sampler_Id s
 ) {
-	instances = (Model_Instance*)arena_alloc(arena, max_instances);
+	int hs;
+	h = (Heap*)arena_alloc(arena, sizeof *h);
+	hs = arena->size - arena->ptr - allocation_default_alignment - 1;
+	init_heap(h, arena_alloc(arena, hs), hs);
+	instances = (Model_Instance*)heap_alloc(h, max_instances);
 	count = 0;
 	max = max_instances;
 	sampler = s;
@@ -417,7 +456,7 @@ Model_Instance* Model_Scene::instantiate(
 ) {
 	Model_Instance* instance = &instances[count++];
 	assert(count <= max);
-	instance->init(dev, model);
+	instance->init(dev, h, model);
 	return instance;
 }
 
@@ -427,7 +466,7 @@ void Model_Scene::uninstantiate(
 ) {
 	int idx = model - instances;
 	int last = count - 1;
-	model->destroy(dev);
+	model->destroy(dev, h);
 	instances[idx] = instances[last];
 	count = last;
 }
@@ -435,8 +474,10 @@ void Model_Scene::uninstantiate(
 void Model_Scene::update(const Camera& cam, Device* dev) {
 	int i;
 	Model_Instance* instance = instances;
-	for (i = 0; i < count; i++, instance++)
+	for (i = 0; i < count; i++, instance++) {
+		instance->update();
 		instance->update_cbuffers(dev, cam);
+	}
 }
 
 void Model_Scene::render(
@@ -456,5 +497,28 @@ void Model_Scene::destroy(Device* dev) {
 	int i;
 	Model_Instance* instance = instances;
 	for (i = 0; i < count; i++, instance++)
-		instance->destroy(dev);
+		instance->destroy(dev, h);
+}
+
+std::pair<Model_Instance*, int> Model_Scene::pick(
+	const Camera& cam,
+	int w,
+	int h,
+	int mx,
+	int my
+) {
+	int i, c = count;
+	v2f uv = (2.0f * v2f(mx, my) - v2f(w, h)) / (float)h;
+	v4f e =
+		cam.get_proj().inverse() *
+		v4f(uv.x, uv.y, -1.0f, 1.0f);
+	e.z = -1.0f; e.w = 0.0f;
+	v4f d4 = cam.get_view().inverse() * e;
+	v3f d = v3f::normalised(v3f(d4.x, d4.y, d4.z));
+	for (i = 0; i < c; i++) {
+		int m = instances[i].pick(cam.position, d);
+		if (m >= 0) return { &instances[i], m };
+	}
+	return { 0, -1 };
 }
+
-- 
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