default/src/RenderTopView.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "RenderTopView.h"

#include "VideoTex.h"
#include "glError.h"
#include "shader.h"
#include "shader_projectedTex.h"
#include "shader_simpleTex.h"

#include <android-base/logging.h>
#include <math/mat4.h>
#include <math/vec3.h>

namespace {

using aidl::android::hardware::automotive::evs::BufferDesc;
using aidl::android::hardware::automotive::evs::IEvsEnumerator;

// Simple aliases to make geometric math using vectors more readable
const unsigned X = 0;
const unsigned Y = 1;
const unsigned Z = 2;

// Since we assume no roll in these views, we can simplify the required math
android::vec3 unitVectorFromPitchAndYaw(float pitch, float yaw) {
    float sinPitch, cosPitch;
    sincosf(pitch, &sinPitch, &cosPitch);
    float sinYaw, cosYaw;
    sincosf(yaw, &sinYaw, &cosYaw);
    return android::vec3(cosPitch * -sinYaw, cosPitch * cosYaw, sinPitch);
}

// Helper function to set up a perspective matrix with independent horizontal and vertical
// angles of view.
android::mat4 perspective(float hfov, float vfov, float near, float far) {
    const float tanHalfFovX = tanf(hfov * 0.5f);
    const float tanHalfFovY = tanf(vfov * 0.5f);

    android::mat4 p(0.0f);
    p[0][0] = 1.0f / tanHalfFovX;
    p[1][1] = 1.0f / tanHalfFovY;
    p[2][2] = -(far + near) / (far - near);
    p[2][3] = -1.0f;
    p[3][2] = -(2.0f * far * near) / (far - near);
    return p;
}

// Helper function to set up a view matrix for a camera given it's yaw & pitch & location
// Yes, with a bit of work, we could use lookAt, but it does a lot of extra work
// internally that we can short cut.
android::mat4 cameraLookMatrix(const ConfigManager::CameraInfo& cam) {
    float sinYaw, cosYaw;
    sincosf(cam.yaw, &sinYaw, &cosYaw);

    // Construct principal unit vectors
    android::vec3 vAt = unitVectorFromPitchAndYaw(cam.pitch, cam.yaw);
    android::vec3 vRt = android::vec3(cosYaw, sinYaw, 0.0f);
    android::vec3 vUp = -cross(vAt, vRt);
    android::vec3 eye = android::vec3(cam.position[X], cam.position[Y], cam.position[Z]);

    android::mat4 Result(1.0f);
    Result[0][0] = vRt.x;
    Result[1][0] = vRt.y;
    Result[2][0] = vRt.z;
    Result[0][1] = vUp.x;
    Result[1][1] = vUp.y;
    Result[2][1] = vUp.z;
    Result[0][2] = -vAt.x;
    Result[1][2] = -vAt.y;
    Result[2][2] = -vAt.z;
    Result[3][0] = -dot(vRt, eye);
    Result[3][1] = -dot(vUp, eye);
    Result[3][2] = dot(vAt, eye);
    return Result;
}

}  // namespace

RenderTopView::RenderTopView(std::shared_ptr<IEvsEnumerator> enumerator,
                             const std::vector<ConfigManager::CameraInfo>& camList,
                             const ConfigManager& mConfig) :
      mEnumerator(enumerator), mConfig(mConfig) {
    // Copy the list of cameras we're to employ into our local storage.  We'll create and
    // associate a streaming video texture when we are activated.
    mActiveCameras.reserve(camList.size());
    for (unsigned i = 0; i < camList.size(); i++) {
        mActiveCameras.emplace_back(camList[i]);
    }
}

bool RenderTopView::activate() {
    // Ensure GL is ready to go...
    if (!prepareGL()) {
        LOG(ERROR) << "Error initializing GL";
        return false;
    }

    // Load our shader programs
    mPgmAssets.simpleTexture =
            buildShaderProgram(vtxShader_simpleTexture, pixShader_simpleTexture, "simpleTexture");
    if (!mPgmAssets.simpleTexture) {
        LOG(ERROR) << "Failed to build shader program";
        return false;
    }
    mPgmAssets.projectedTexture =
            buildShaderProgram(vtxShader_projectedTexture, pixShader_projectedTexture,
                               "projectedTexture");
    if (!mPgmAssets.projectedTexture) {
        LOG(ERROR) << "Failed to build shader program";
        return false;
    }

    // Load the checkerboard text image
    mTexAssets.checkerBoard.reset(
            createTextureFromPng("/system/etc/automotive/evs/LabeledChecker.png"));
    if (!mTexAssets.checkerBoard) {
        LOG(ERROR) << "Failed to load checkerboard texture";
        return false;
    }

    // Load the car image
    mTexAssets.carTopView.reset(createTextureFromPng("/system/etc/automotive/evs/CarFromTop.png"));
    if (!mTexAssets.carTopView) {
        LOG(ERROR) << "Failed to load carTopView texture";
        return false;
    }

    // Set up streaming video textures for our associated cameras
    for (auto&& cam : mActiveCameras) {
        cam.tex.reset(
                createVideoTexture(mEnumerator, cam.info.cameraId.c_str(), nullptr, sDisplay));
        if (!cam.tex) {
            LOG(ERROR) << "Failed to set up video texture for " << cam.info.cameraId << " ("
                       << cam.info.function << ")";
            return false;
        }
    }

    return true;
}

void RenderTopView::deactivate() {
    // Release our video textures
    // We can't hold onto it because some other Render object might need the same camera
    for (auto&& cam : mActiveCameras) {
        cam.tex = nullptr;
    }
}

bool RenderTopView::drawFrame(const BufferDesc& tgtBuffer) {
    // Tell GL to render to the given buffer
    if (!attachRenderTarget(tgtBuffer)) {
        LOG(ERROR) << "Failed to attached render target";
        return false;
    }

    // Set up our top down projection matrix from car space (world units, Xfwd, Yright, Zup)
    // to view space (-1 to 1)
    const float top = mConfig.getDisplayTopLocation();
    const float bottom = mConfig.getDisplayBottomLocation();
    const float right = mConfig.getDisplayRightLocation(sAspectRatio);
    const float left = mConfig.getDisplayLeftLocation(sAspectRatio);

    const float near = 10.0f;  // arbitrary top of view volume
    const float far = 0.0f;    // ground plane is at zero

    // We can use a simple, unrotated ortho view since the screen and car space axis are
    // naturally aligned in the top down view.
    orthoMatrix = android::mat4::ortho(left, right, top, bottom, near, far);

    // Refresh our video texture contents.  We do it all at once in hopes of getting
    // better coherence among images.  This does not guarantee synchronization, of course...
    for (auto&& cam : mActiveCameras) {
        if (cam.tex) {
            cam.tex->refresh();
        }
    }

    // Iterate over all the cameras and project their images onto the ground plane
    for (auto&& cam : mActiveCameras) {
        renderCameraOntoGroundPlane(cam);
    }

    // Draw the car image
    renderCarTopView();

    // Now that everythign is submitted, release our hold on the texture resource
    detachRenderTarget();

    // Wait for the rendering to finish
    glFinish();
    detachRenderTarget();
    return true;
}

//
// Responsible for drawing the car's self image in the top down view.
// Draws in car model space (units of meters with origin at center of rear axel)
// NOTE:  We probably want to eventually switch to using a VertexArray based model system.
//
void RenderTopView::renderCarTopView() {
    // Compute the corners of our image footprint in car space
    const float carLengthInTexels = mConfig.carGraphicRearPixel() - mConfig.carGraphicFrontPixel();
    const float carSpaceUnitsPerTexel = mConfig.getCarLength() / carLengthInTexels;
    const float textureHeightInCarSpace = mTexAssets.carTopView->height() * carSpaceUnitsPerTexel;
    const float textureAspectRatio =
            (float)mTexAssets.carTopView->width() / mTexAssets.carTopView->height();
    const float pixelsBehindCarInImage =
            mTexAssets.carTopView->height() - mConfig.carGraphicRearPixel();
    const float textureExtentBehindCarInCarSpace = pixelsBehindCarInImage * carSpaceUnitsPerTexel;

    const float btCS = mConfig.getRearLocation() - textureExtentBehindCarInCarSpace;
    const float tpCS = textureHeightInCarSpace + btCS;
    const float ltCS = 0.5f * textureHeightInCarSpace * textureAspectRatio;
    const float rtCS = -ltCS;

    GLfloat vertsCarPos[] = {
            ltCS, tpCS, 0.0f,  // left top in car space
            rtCS, tpCS, 0.0f,  // right top
            ltCS, btCS, 0.0f,  // left bottom
            rtCS, btCS, 0.0f   // right bottom
    };
    // NOTE:  We didn't flip the image in the texture, so V=0 is actually the top of the image
    GLfloat vertsCarTex[] = {
            0.0f, 0.0f,  // left top
            1.0f, 0.0f,  // right top
            0.0f, 1.0f,  // left bottom
            1.0f, 1.0f   // right bottom
    };
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, vertsCarPos);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, vertsCarTex);
    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glUseProgram(mPgmAssets.simpleTexture);
    GLint loc = glGetUniformLocation(mPgmAssets.simpleTexture, "cameraMat");
    glUniformMatrix4fv(loc, 1, false, orthoMatrix.asArray());
    glBindTexture(GL_TEXTURE_2D, mTexAssets.carTopView->glId());

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisable(GL_BLEND);

    glDisableVertexAttribArray(0);
    glDisableVertexAttribArray(1);
}

// NOTE:  Might be worth reviewing the ideas at
// http://math.stackexchange.com/questions/1691895/inverse-of-perspective-matrix
// to see if that simplifies the math, although we'll still want to compute the actual ground
// interception points taking into account the pitchLimit as below.
void RenderTopView::renderCameraOntoGroundPlane(const ActiveCamera& cam) {
    // How far is the farthest any camera should even consider projecting it's image?
    const float visibleSizeV = mConfig.getDisplayTopLocation() - mConfig.getDisplayBottomLocation();
    const float visibleSizeH = visibleSizeV * sAspectRatio;
    const float maxRange = (visibleSizeH > visibleSizeV) ? visibleSizeH : visibleSizeV;

    // Construct the projection matrix (View + Projection) associated with this sensor
    const android::mat4 V = cameraLookMatrix(cam.info);
    const android::mat4 P =
            perspective(cam.info.hfov, cam.info.vfov, cam.info.position[Z], maxRange);
    const android::mat4 projectionMatix = P * V;

    // Just draw the whole darn ground plane for now -- we're wasting fill rate, but so what?
    // A 2x optimization would be to draw only the 1/2 space of the window in the direction
    // the sensor is facing.  A more complex solution would be to construct the intersection
    // of the sensor volume with the ground plane and render only that geometry.
    const float top = mConfig.getDisplayTopLocation();
    const float bottom = mConfig.getDisplayBottomLocation();
    const float wsHeight = top - bottom;
    const float wsWidth = wsHeight * sAspectRatio;
    const float right = wsWidth * 0.5f;
    const float left = -right;

    const android::vec3 topLeft(left, top, 0.0f);
    const android::vec3 topRight(right, top, 0.0f);
    const android::vec3 botLeft(left, bottom, 0.0f);
    const android::vec3 botRight(right, bottom, 0.0f);

    GLfloat vertsPos[] = {
            topLeft[X], topLeft[Y], topLeft[Z], topRight[X], topRight[Y], topRight[Z],
            botLeft[X], botLeft[Y], botLeft[Z], botRight[X], botRight[Y], botRight[Z],
    };
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, vertsPos);
    glEnableVertexAttribArray(0);

    glDisable(GL_BLEND);

    glUseProgram(mPgmAssets.projectedTexture);
    GLint locCam = glGetUniformLocation(mPgmAssets.projectedTexture, "cameraMat");
    glUniformMatrix4fv(locCam, 1, false, orthoMatrix.asArray());
    GLint locProj = glGetUniformLocation(mPgmAssets.projectedTexture, "projectionMat");
    glUniformMatrix4fv(locProj, 1, false, projectionMatix.asArray());

    GLuint texId;
    if (cam.tex) {
        texId = cam.tex->glId();
    } else {
        texId = mTexAssets.checkerBoard->glId();
    }
    glBindTexture(GL_TEXTURE_2D, texId);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisableVertexAttribArray(0);
}