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/* SPDX-License-Identifier: MIT */
/*
* konrender.h
*
* Copyright (c) 2026 KonAki
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef KONRENDER_H
#define KONRENDER_H
#include "konmath.h"
#include "konsofren.h"
typedef enum kon_projection {
KON_PROJECTION_PERSPECTIVE = 0,
KON_PROJECTION_ORTHOGRAPHIC
} kon_projection_t;
typedef struct kon_camera {
kon_vec3_t position;
kon_vec3_t target;
kon_vec3_t up;
kon_projection_t projection;
float fov; /* vertical field of view in radians, perspective only */
float orthoSize; /* half the visible height in world units, orthographic only */
float nearZ, farZ;
} kon_camera_t;
/* edges holds pairs of indices into vertices */
typedef struct kon_wireMesh {
const kon_vec3_t *vertices;
const uint16_t *edges;
int edgeCount;
} kon_wireMesh_t;
/*** camera declarations ***/
kon_camera_t kon_cameraDefault(void);
kon_mat4_t kon_cameraView(const kon_camera_t *camera);
kon_mat4_t kon_cameraProjection(const kon_camera_t *camera, int width, int height);
kon_mat4_t kon_cameraViewProjection(const kon_camera_t *camera, int width, int height);
/*** draw declarations ***/
/* returns 0 if the point is behind the camera */
int kon_worldToScreen(const kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_vec3_t point, kon_vec2_t *out);
void kon_drawLine3D(kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_vec3_t a, kon_vec3_t b, uint32_t color);
void kon_drawWireMesh(kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_mat4_t model, const kon_wireMesh_t *mesh, uint32_t color);
/*** implementation ***/
#ifdef KONRENDER_IMPLEMENTATION
/*** private helper ***/
static kon_vec2_t kon_clipToScreen_(const kon_framebuffer_t *fb, kon_vec4_t clip) {
/* clamped so the later float to int conversion can't overflow */
float ndcX = kon_clamp(clip.x / clip.w, -1.0e5f, 1.0e5f);
float ndcY = kon_clamp(clip.y / clip.w, -1.0e5f, 1.0e5f);
/* screen +Y points down, NDC +Y points up */
return KON_VEC2((ndcX + 1.0f) * 0.5f * (float)fb->width, (1.0f - ndcY) * 0.5f * (float)fb->height);
}
/*** camera implementation ***/
kon_camera_t kon_cameraDefault(void) {
kon_camera_t camera;
camera.position = KON_VEC3(0, 0, 5);
camera.target = KON_VEC3_ZERO;
camera.up = KON_VEC3_UP;
camera.projection = KON_PROJECTION_PERSPECTIVE;
camera.fov = KON_DEG2RAD(60);
camera.orthoSize = 5.0f;
camera.nearZ = 0.1f;
camera.farZ = 100.0f;
return camera;
}
kon_mat4_t kon_cameraView(const kon_camera_t *camera) {
return kon_mat4LookAt(camera->position, camera->target, camera->up);
}
kon_mat4_t kon_cameraProjection(const kon_camera_t *camera, int width, int height) {
float aspect = (height > 0) ? (float)width / (float)height : 1.0f;
if (camera->projection == KON_PROJECTION_ORTHOGRAPHIC) {
float halfH = camera->orthoSize;
float halfW = halfH * aspect;
return kon_mat4Ortho(-halfW, halfW, -halfH, halfH, camera->nearZ, camera->farZ);
}
return kon_mat4Perspective(camera->fov, aspect, camera->nearZ, camera->farZ);
}
kon_mat4_t kon_cameraViewProjection(const kon_camera_t *camera, int width, int height) {
return kon_mat4Mul(kon_cameraProjection(camera, width, height), kon_cameraView(camera));
}
/*** draw implementation ***/
int kon_worldToScreen(const kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_vec3_t point, kon_vec2_t *out) {
if (!fb || !out) return 0;
kon_vec4_t clip = kon_mat4MulVec4(viewProjection, KON_VEC4(point.x, point.y, point.z, 1));
/* in front of the near plane when z >= -w */
if (clip.z < -clip.w || clip.w <= 0.0f) return 0;
*out = kon_clipToScreen_(fb, clip);
return 1;
}
void kon_drawLine3D(kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_vec3_t a, kon_vec3_t b, uint32_t color) {
if (!fb) return;
kon_vec4_t ca = kon_mat4MulVec4(viewProjection, KON_VEC4(a.x, a.y, a.z, 1));
kon_vec4_t cb = kon_mat4MulVec4(viewProjection, KON_VEC4(b.x, b.y, b.z, 1));
/* clip against the near plane (z + w >= 0) before dividing, so points behind the camera never get projected */
float da = ca.z + ca.w;
float db = cb.z + cb.w;
if (da < 0.0f && db < 0.0f) return;
if (da < 0.0f || db < 0.0f) {
float t = da / (da - db);
kon_vec4_t hit = KON_VEC4(
ca.x + (cb.x - ca.x) * t,
ca.y + (cb.y - ca.y) * t,
ca.z + (cb.z - ca.z) * t,
ca.w + (cb.w - ca.w) * t
);
if (da < 0.0f) ca = hit;
else cb = hit;
}
if (ca.w <= 0.0f || cb.w <= 0.0f) return;
kon_vec2_t sa = kon_clipToScreen_(fb, ca);
kon_vec2_t sb = kon_clipToScreen_(fb, cb);
kon_drawLine(fb, (int)sa.x, (int)sa.y, (int)sb.x, (int)sb.y, color);
}
void kon_drawWireMesh(kon_framebuffer_t *fb, kon_mat4_t viewProjection, kon_mat4_t model, const kon_wireMesh_t *mesh, uint32_t color) {
if (!fb || !mesh) return;
kon_mat4_t mvp = kon_mat4Mul(viewProjection, model);
for (int i = 0; i < mesh->edgeCount; i++) {
kon_vec3_t a = mesh->vertices[mesh->edges[i * 2 + 0]];
kon_vec3_t b = mesh->vertices[mesh->edges[i * 2 + 1]];
kon_drawLine3D(fb, mvp, a, b, color);
}
}
#endif /* end of KONRENDER_IMPLEMENTATION */
#endif
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